Memory device, host circuit, circuit board, liquid receptacle, method of transmitting data stored in a nonvolatile data memory section to a host circuit, and system including a host circuit and a memory device detachably attachable to the host circuit

ABSTRACT

A memory device is electrically connectable to a host circuit. The memory device includes a nonvolatile data memory section, a read/write control section, and a data transmission section. The read/write control section reads a first data from the nonvolatile data memory section where the first data has a prescribed data amount. The data transmission section transmits to the host circuit the first data together with second data, wherein the second data is different from the first data and has prescribed correlation with content of the first data. The second data having an identical data amount to the data amount of the first data.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application claims the priority based on Japanese PatentApplication No. 2009-088592 filed on Apr. 1, 2009, the disclosure ofwhich is hereby incorporated by reference in their entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a memory device, to a host circuit, toa circuit board, to a liquid receptacle, to a method of transmittingdata stored in a nonvolatile data memory section to a host circuit, andto a system that includes a host circuit and a memory device detachablyattachable to the host circuit.

2. Description of the Related Art

An inkjet printer, which is one example of a liquid ejecting device,typically has one or more installed ink receptacles or ink containerswhich are detachable liquid receptacles. Some ink receptacles areprovided with memory devices. The memory device stores information ofvarious kinds, for example, the remaining ink level or the color of theink in the ink receptacle. A control unit provided to the printercommunicates with the memory device of the ink receptacle.

JP-A 2002-370383

JP-A 2004-299405

JP-A 2001-146030

JP-A 6-226989

JP-A 2003-112431

However, in conventional techniques, insufficient consideration wasgiven to the issue of dependability of communication between the controlunit provided to the printer and the memory devices provided to the inkreceptacles. For example, there is a risk that, for reasons such asfaulty contact between the electrical contact portions of the printerand an ink receptacle, faulty communication may occur between thecontrol unit provided to the printer and the memory device of the inkreceptacle. If operation of the print control unit were to continue onwith the faulty communication unresolved, there is a risk of problemssuch as errors being created in the memory contents of the memorydevice. This issue is not limited to memory devices provided to inkreceptacles, but is rather an issue common to all manner of memorydevices that electrically connect to a host circuit.

SUMMARY OF THE INVENTION

An object of the present invention is to provide a technology forimproving dependability of communication with a host circuit in a memorydevice that is electrically connected to the host circuit.

The present invention is addressed to attaining the above objects atleast in part according to the following aspects or modes of the presentinvention.

A first aspect of the present invention is directed to a memory deviceelectrically connectable to a host circuit. The memory device includes anonvolatile data memory section; a read/write control section that readsa first data from the nonvolatile data memory section, the first datahaving a prescribed data amount; and a data transmission section thattransmits to the host circuit the first data together with second data,wherein the second data is different from the first data and hascorrelation with content of the first data, the second data having anidentical data amount to the data amount of the first data.

With this arrangement, the host circuit can judge the communicationcondition by determining the correlation between the first data and thesecond data. As a result, dependability of communication between thehost circuit and the memory device is enhanced.

In a second aspect of the present invention, the memory device furtherincludes a data generation section that generates the second data usingthe first data. With this arrangement, the memory device can generatethe second data using the first data.

In a third aspect of the present invention, the first data and thesecond data each are binary signals of n bits where n is an integerequal to or greater than 1, and the second data is inverted data thatinverts each bit of the first data. With this arrangement, since thesecond data is inverted data of the first data, if, for example, onlyone level of the binary signals appears on the communication line due tocommunication errors, the host circuit can surely detect thecommunication errors.

In a fourth aspect of the present invention, the integer n is an evennumber, and the data transmission section transmits, in synchronism witha clock signal, an upper n/2 bits of the first data, an upper n/2 bitsof the second data, a lower n/2 bits of the first data, and a lower n/2bits of the second data, in that order.

In a fifth aspect of the present invention, the data transmissionsection additionally transmits to the host circuit third data that issubstantially identical to the first data, and fourth data that issubstantially identical to the second data. With this arrangement, thehost circuit can continue processing using the fourth data even if thefirst data includes communication errors.

In a sixth aspect of the present invention, the nonvolatile data memorysection has a first memory area for storing the first data, and a secondmemory area for storing the third data. With this arrangement, the hostcircuit can obtain the third data as correct data which is stored in thesecond memory area even if there are some memory defects in the firstmemory area.

In a seventh aspect of the present invention, the memory device furtherincludes a data generation section that generate the second data fromthe first data, and to generate the fourth data from the third data.With this arrangement, the host circuit can continue processing usingdata having the prescribed correlation after confirming if there existsthe prescribed correlation between the first and second data, or betweenthe third and fourth data.

In a eighth aspect of the present invention, the first data, the seconddata, the third data, and the fourth data each are binary signals of mbits where m is an integer equal to or greater than 1; the third data iscopy data copied from the first data, the second data is inverted datathat inverts each bit of the first data, and the fourth data is inverteddata that inverts each bit of the third data. With this arrangement,since the second and the fourth data are inverted data of the first andthird data, if, for example, only one level of the binary signalsappears on the communication line due to communication errors, the hostcircuit can surely detect the communication errors.

In a ninth aspect of the present invention, the integer m is an evennumber, and the data transmission section transmits, in synchronism witha clock signal, an upper m/2 bits of the first data, an upper m/2 bitsof the second data, a lower m/2 bits of the first data, a lower m/2 bitsof the second data, an upper m/2 bits of the third data, an upper m/2bits of the fourth data, a lower m/2 bits of the third data, and a lowerm/2 bits of the fourth data, in that order.

In a tenth aspect of the present invention, a data generation sectionthat generates the second data, the third data, and the fourth data fromthe first data. With this arrangement, the second memory area may beomitted, whereby it is possible to reduce memory capacity.

In a eleventh aspect of the present invention, a first memory area forstoring the first data, and a second memory area for storing the thirddata. With this arrangement, the host circuit can obtain the second dataas correct data which is stored in the second memory area even if thereare some memory defects in the first memory area.

In a twelfth aspect of the present invention, a data generation sectionthat generates the third data from the first data, and generates thefourth data from the second data. With this arrangement, the hostcircuit can continue processing using data having the prescribedcorrelation after confirming if there exists the prescribed correlationbetween the first and second data, or between the third and fourth data.

In a thirteenth aspect of the present invention, the host circuit andthe memory device are adapted to be electrically connected viacircuit-side terminals that are electrically connected to the hostcircuit, and memory-device-side terminals that are electricallyconnected to the memory device and detachably attachable to thecircuit-side terminals. With this arrangement, communication errors dueto contact failure between the memory-device-side terminals and thecircuit-side terminals can be detected, and the dependability ofcommunication between the host circuit and the memory device is enhancedaccordingly.

A fourteenth aspect of the present invention is directed to a hostcircuit electrically connectable to the memory device. The host circuitincludes a data reception section that receives the first data and thesecond data from the memory device; and a determination section thatdetermines whether the first data and the second data have theprescribed correlation. With this arrangement, the host circuit candetermine if there exists a communication error between the host circuitand the memory device.

A fifteenth aspect of the present invention is directed to a hostcircuit electrically connectable to the memory device. The hose circuitincludes a data reception section that receives the first data and thesecond data from the memory device; and a determination section thatoutputs an affirmative determination result if an exclusive OR outcomeof an m-th value of the first data and an m-th value in the second datais true for all the n bits where m is an integer such that 1≦m≦n; andoutputs a negative determination result if the exclusive OR outcome isfalse for any one of the n bits. With this arrangement, if, for example,only one level of the binary signals appears on the communication linedue to communication errors, the host circuit can surely detect thecommunication errors.

A sixteenth aspect of the present invention is directed to a hostcircuit electrically connectable to the memory device. The host circuitincludes a data reception section that receives the first data, thesecond data, the third data, and the fourth data from the memory device;and a first determination section that carries out a first determinationto output an affirmative determination result if an exclusive OR outcomeof a k-th value of the first data and a k-th value of the fourth data istrue for all the m bits where k is an integer such that 1≦k≦m, or tooutput a negative determination result if the exclusive OR outcome isfalse for any one of the m bits. With this arrangement, the host circuitcan determine if there exists a communication error between the hostcircuit and the memory device, or a memory defect in the data memorysection.

In a seventeenth aspect of the present invention, the host circuitfurther includes a second determination section that carries out asecond determination in instances where the determination result of thefirst determination is negative. The second determination sectiondetermines that an error has occurred in the nonvolatile data memorysection of the memory device if an exclusive OR outcome of a k-th valueof the first data and a k-th value of the second data is true for allthe m bits, and also an exclusive OR outcome of a k-th value of thethird data and a k-th value of the fourth data is true for all the mbits, and the second determination section determines that acommunication error has occurred between the memory device and the hostcircuit if the exclusive OR outcome of the k-th value of the first dataand the k-th value of the second data is false for any one of the mbits, or if the exclusive OR outcome of the k-th value of the third dataand the k-th value of the fourth data is false for any one of the mbits. With this arrangement, the host circuit can properly detect a datamemory section error and a communication error, respectively.

It is possible for the present invention to be embodied in variousmodes, for example, a circuit board detachably and electricallyconnectable to a liquid ejecting device; a liquid receptacle detachablyinstallable in a liquid ejecting device; a method of transmitting datastored in a data memory section to a host circuit; a system thatincludes a host circuit and a memory device detachably installable tothe host circuit; a liquid ejecting system; a computer program foraccomplishing the functions of such methods or devices; or a recordingmedium having such a computer program recorded thereon.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates a simplified configuration of a printing system;

FIGS. 2A and 2B are perspective views depicting a configuration of anink cartridge according to the embodiment;

FIGS. 3A and 3B depict a configuration of a board according to theembodiment;

FIG. 4 illustrates a configuration of a print head unit;

FIG. 5 is a first illustration depicting an electrical configuration ofa printer;

FIG. 6 is a second illustration depicting an electrical configuration ofa printer;

FIG. 7 schematically depicts a memory map of memory areas provided by aferroelectric memory array of a memory device;

FIG. 8 is a flowchart depicting a processing routine of a read operationfrom a memory device on the printer;

FIG. 9 is a timing chart schematically depicting signals exchangedbetween a communication process module and a memory control circuitduring a read operation from a memory device;

FIG. 10 is a flowchart schematically depicting a processing routine of aread operation from a memory device on the memory;

FIG. 11 is a flowchart depicting the processing routine of a readoperation taking place on the memory device;

FIG. 12 is a flowchart depicting the processing routine of a writeoperation to a memory device taking place on the printer;

FIG. 13 schematically depicts a memory map recognized on the printerduring a write operation to a memory device;

FIG. 14 is a timing chart schematically depicting signals exchangedbetween a communication process module and a memory control circuitduring a write operation to a memory device;

FIG. 15 is a flowchart depicting the processing routine of a writeoperation in a memory device;

FIG. 16 is a timing chart schematically depicting signals exchangedbetween a communication process module and a memory control circuitduring a write lock operation of a memory device; and

FIG. 17 is a flowchart depicting the process steps in a printingoperation.

DESCRIPTION OF THE PREFERRED EMBODIMENT A. Embodiment Configuration ofPrinting System

FIG. 1 is an illustration depicting a simplified configuration of aprinting system. The printing system includes a printer 20 provided asthe printing device, and a computer 90. The printer 20 is connected tothe computer 90 via a connector 80.

The printer 20 is furnished with a sub-scanning feed mechanism, a mainscanning feed mechanism, a head driving mechanism, and a main controller40. The sub-scanning feed mechanism has a paper feed motor 22 and aplaten 26, and conveys paper PA in the sub-scanning direction bytransmitting rotation of the paper feed motor to the platen. The mainscanning feed mechanism includes a carriage motor 32, a pulley 38, adrive belt 36 stretched between the carriage motor and the pulley, and aslide rail 34 disposed parallel to the axis of the platen 26. The sliderail 34 slidably retains a carriage 30 that is affixed to the drive belt36. Rotation of the carriage motor 32 is transmitted to the carriage 30via the drive belt 36, whereupon the carriage 30 undergoes reciprocatingmovement in the axial direction of the platen 26 (the main scanningdirection) along the slide rail 34. The head driving mechanism includesa print head unit 60 installed on the carriage 30, and is designed todrive a print head and eject ink onto the paper PA. The main controller40 controls the above mechanisms and carries out printing operations.The main controller 40 for example receives a print job from a user viathe computer 90, and control the above mechanisms to carry out printingbased on the content of the received print job. As will be discussedlater, a plurality of ink cartridges are detachably installable in theprint head unit 60. Specifically, ink cartridges for supplying ink tothe print head are disposed in the print head unit 60 in such a way asto be attachable and detachable through user operation. The printer 20also has a console portion 70 allowing the use to perform variousprinter settings, check printer status, and so on.

The configuration of the printer, together with the configuration of anink cartridge (liquid receptacle), will be discussed further withreference to FIGS. 2A, 2B, 3A, 3B, and 4. FIGS. 2A and 2B areperspective views depicting a configuration of an ink cartridgeaccording to the embodiment. FIGS. 3A and 3B are drawings depicting aconfiguration of a printed circuit board (hereinafter termed simply acircuit board) according to the embodiment. FIG. 4 is a drawingillustrating a configuration of the print head unit 60.

The ink cartridge 100 has a main body 101 for containing the ink, acircuit board 120, and a sensor 110. On the base face of the main body101 there is provided an ink delivery port 104 that, with the cartridgeinstalled in the print head unit 60, delivers ink to the print head unit60. An ink chamber 150 for containing the ink is formed in the main body101. The ink delivery port 104 communicates with the ink chamber 150.The opening 104 op of the ink delivery port 104 is sealed by a film 104f. By installing the ink cartridge 100 on the print head unit 60 (FIG.4), the film 104 f punctures and an ink delivery needle 6 insertsthrough the ink delivery port 104 (FIG. 4). The ink contained in the inkchamber 150 is delivered to the printer 20 through the ink deliveryneedle 6.

The sensor 110 is secured to the inside of the main body 101. As will bediscussed later, the sensor 110 includes a piezoelectric elementcomposed of a piezoelectric body sandwiched between two opposedelectrodes, and is used for detecting the remaining ink level. The mainbody 101 includes a front wall 101 wf (wall lying in the −Y direction)and a base wall 101 wb (wall lying in the +Z direction). The front wall101 wf intersects (in the present embodiment, at a substantially rightangle) the base wall 101 wb. The circuit board 120 is secured to thefront wall 101 wf. The outside surface of the circuit board 120 isprovided with terminals 210 to 270.

Two projections P1, P2 are formed on the front wall 101 wf. Theseprojections P1, P2 project out in the −Y direction. A hole 122 and anotch 121 adapted to respectively receive these projections P1, P2 areformed in the circuit board 120 (FIG. 3A). The hole 122 is formed in thecenter of the edge of the circuit board 120 on the ink delivery port 104side (the +Z direction edge) thereof, while the notch 121 is formed inthe center of the edge of the circuit board 120 on the opposite sidefrom the ink delivery port 104 (the −Z direction edge). With the circuitboard 120 mounted onto the front wall 101 wf, the projections P1, P2pass respectively through the hole 122 and the notch 121. Duringproduction of the ink cartridge 100, after the circuit board 120 ismounted on the front wall 101 wf, the tips of these projections P1, P2is collapsed. The circuit board 120 is secured thereby to the front wall101 wf.

Additionally, a mating projection 101 e is provided in the front wall101 wf. The ink cartridge 100 is prevented from inadvertently detachingfrom the holder 4 through mating of the mating projection 101 e and amating aperture 4 e of a holder 4 (FIG. 4).

The configuration of the print head unit 60, as well as installation ofthe ink cartridge 100 in the print head unit 60, is discussed withreference to FIG. 4. As depicted in FIG. 4, the print head unit 60includes a holder 4, a connection mechanism 400, a print head 5, and asub-control board 500. On the sub-control board 500 there are mounted acarriage circuit 50 and a group of terminals for respective connectionvia the connection mechanism 400 to the individual terminals 210 to 270of the circuit board 120 of the ink cartridge 100. The holder 4 isdesigned to receive installation of several ink cartridges 100, and issituated on top of the print head 5. The connection mechanism 400 haselectrically conductive connection terminals 410 to 470 provided foreach of the terminals of the circuit board 120 and adapted to provideelectrical connections between the terminals of the circuit board 120 ofthe ink cartridge 100, discussed later, and the terminals disposed onthe sub-control board 500. The aforementioned ink delivery needles 6 fordelivering ink from the ink cartridges 100 to the print head 5 aresituated on the print head 5. The print head 5 includes several nozzlesand several piezoelectric elements, and is adapted to eject droplets ofink from the nozzles in response to voltage applied to the piezoelectricelements, thereby producing dots on the paper PA. The carriage circuit50 is a circuit designed to carry out control in relation to the inkcartridges 100 in concert with the main controller 40, and herein isalso referred to as the sub-controller.

The ink cartridge 100 is installed in the holder 4 by inserting it inthe Z-axis forward direction (the insertion direction R) in FIG. 4. Theink cartridge 100 is thereby detachably installed in the printer 20. Thecircuit board 120 which is mounted onto the ink cartridge 100 isinstalled in or uninstalled from the printer 20 in association withinstallation or uninstallation of the ink cartridge 100 by the user.When the ink cartridge 100 is installed in the printer 20, the circuitboard 120 is electrically coupled with the printer 20.

The description of the circuit board 120 continues, returning to FIGS.3A and 3B. The arrow R in FIG. 3A indicates the ink cartridge 100insertion direction mentioned above. As shown in FIG. 3B, the circuitboard 120 is provided with a memory device 130 on its back face, i.e.the face to the back side of the face that connects with the printer 20;and is provided with a terminal group composed of seven terminals on itsfront face, i.e. the face that connects with the printer 20. In thepresent embodiment, the memory device 130 is a semiconductor memorydevice that includes a ferroelectric memory cell array. This memory cellarray, which corresponds to the data memory section of the presentinvention, stores data of various kinds relating to the ink cartridge100 or to the ink, such as ink consumption, ink color, and so on. Theink consumption data indicates, for the ink contained in the inkcartridge in question, the cumulative total amount of ink consumed inthe course of printing and in cleaning of the head. The data mayrepresent the amount of ink per se, or represent the consumed ink as apercentage of a reference amount which is equivalent to the amount ofink initially contained in the ink cartridge.

The terminals on the front side of the circuit board 120 are formed withgenerally rectangular shape and placed so as to form two rowsapproximately orthogonal to the insertion direction R. Of these tworows, the row situated towards the insertion direction R (the distaledge side in the insertion direction when inserted), i.e. to the lowerside in FIG. 3A, is termed the lower row; and the row situated to theopposite side from the insertion direction R, i.e. to the upper side inFIG. 3A, is termed the upper row. Here, the term “lower” is used forconvenience for the purpose of description in terms of FIGS. 3A and 3B.The terminals which form the upper row and the terminals which form thelower row are configured in a so-called staggered arrangement throughmutually different placement, so that the terminal centers are not linedup in the insertion direction R.

The terminals which are arrayed to form the upper row are, in order fromthe left in FIG. 3A, a ground terminal 210 and a power terminal 220. Theterminals which are arrayed to form the lower row are, in order from theleft in FIG. 3A, a first sensor drive terminal 230, a reset terminal240, a clock terminal 250, a data terminal 260, and a second sensordrive terminal 270. The five terminals situated close to the center inthe sideways direction, i.e. the ground terminal 210, the power terminal220, the reset terminal 240, the clock terminal 250, and the dataterminal 260, are respectively connected to the memory device 130 viacircuit pattern layers (not shown) provided on the front and back facesof the circuit board 120, and through-holes situated in the circuitboard 120. The two terminals situated at the ends of the lower row, i.e.the first sensor drive terminal 230 and the second sensor drive terminal270, are respectively connected to one and the other of the electrodesof the piezoelectric element included in the sensor 110.

With this circuit board 120, the five terminals that are connected tothe memory device 130 and the two terminals that are connected to thesensor 110 are situated in proximity to one another. Thus, in theconnection mechanism 400 on the printer 20 side as well, the connectionterminals 410, 420 and 440 to 460 that correspond to the five terminalsconnected to the memory device 130 and the connection terminals 430, 470that correspond to the two terminals connected to the sensor 110 arelikewise situated in proximity to one another.

With the ink cartridge 100 secured in the holder 4, the terminals of thecircuit board 120 are electrically connected through contact with theconnection terminals 410 to 470 of the connection mechanism 400.Additionally, the connection terminals 410 to 470 of the connectionmechanism 400 are electrically connected through contact with theterminal group on the sub-control board 500; and the terminal group onthe sub-control board 500 are in electrical connection withsub-controller (carriage circuit 50). Thus, when the ink cartridge 100is secured in the holder 4, the terminals 210 to 270 of the circuitboard 120 are in electrical connection with the sub-controller 50.

Electrical Configuration of Printer:

FIGS. 5 and 6 are illustrations depicting the electrical configurationof the printer. The illustration in FIG. 5 is focused on the totality ofthe main control circuit 40, the sub-controller 50, and all of the inkcartridges 100 installable in the printer. FIG. 6 depicts the functionalfeatures of the main control circuit 40 and the functional features ofthe sub-controller 50, shown together with a single ink cartridge 100.The sub-controller 50 in the present embodiment corresponds to the hostcircuit of the present invention. In the present embodiment, thesub-controller 50 provided as the host circuit supplies power to thememory device 130 provided as the data memory section, and transmitscommands indicating various types of access to the memory device 130 inorder to write data to the memory device 130 or read data from thememory device 130 (discussed later).

The memory device 130 of each ink cartridge 100 is assigned an 8-bit IDnumber (identification information) different from all the others.Because as shown in FIG. 5 the memory devices 130 of the ink cartridgesare parallel-connected to lines from the sub-controller 50 (i.e. theyare bus-connected to the sub-controller 50), if an operation such as aread/write operation is to be carried out by the sub-controller 50 onthe memory device 130 of a particular ink cartridge 100, it is necessaryfor the particular ink cartridge to be identified from the maincontroller 40 and the sub-controller 50. The ID number is used for thispurpose. This ID number is used by the sub-controller 50 to specify amemory device 130 (ink cartridge 100) that is to be accessed.

The lines that electrically connect the sub-controller 50 with each inkcartridge 100 include the lines connecting the sub-controller 50 withthe terminal group of the sub-control board 500; the connectionterminals 410 to 470 of the connection mechanism 400; the terminal groupon the front side of the circuit board 120; and the lines leading fromthe terminal group of the circuit board 120 to the memory device 130 andto the sensor 110. The lines that electrically connect thesub-controller 50 with each ink cartridge 100 include a reset signalline LR1, a clock signal line LC1, a data signal line LD1, a firstground line LCS, a first power line LCV, a first sensor drive signalline LDSN, and a second sensor drive signal line LDSP.

The reset signal line LR1 between the sub-controller 50 and the memorydevice 130 is a conductive line for sending a reset signal CRST from thesub-controller 50 to the memory device 130. The reset signal is a signalby which the sub-controller 50 may place the memory control circuit 136(discussed later) of a memory device 130 in the initialized state, or ina standby state in which it can accept access. When a low level resetsignal is presented to a memory control circuit 136 by thesub-controller 50, the memory control circuit 136 goes into theinitialized state. The clock signal line LC1 between the sub-controller50 and the memory device 130 is a conductive line for sending a clocksignal CSCK from the sub-controller 50 to the memory device 130. Thedata signal line LD1 between the sub-controller 50 and the memory device130 is a conductive line for sending data signals CSDA that areexchanged between the sub-controller 50 to the memory device 130. Asshown in FIG. 6, in the sub-controller 50, the data signal line LD1 isconnected to ground potential CVSS (0 V) via a pull-down resistor R1. Asa result, potential on the data signal line LD1 is held at low level,particularly when data signals are not being exchanged between thesub-controller 50 and the memory device 130. In order to achievesynchronization between the sub-controller 50 and the memory device 130,data signals are transmitted and received in sync with the clock signalmentioned above. For example, the exchange may take place such thatsignals are transmitted or received while a rise or fall of the clocksignal is used as a valid data timing. Each of these three lines LR1,LC1, LD1 is a line having a single terminus at the sub-controller 50,and branched termini, corresponding in number to the number of inkcartridges 100, at the ink cartridge 100. That is, with respect to thethree lines LR1, LC1, LD1, the plurality of memory devices 130 arebus-connected to the sub-controller 50. The reset signal CRST, the datasignal CSDA, and the clock signal CSCK are all binary signals that haveeither high level (in the present embodiment, CVDD potential of 3.3 V)or low level (in the present embodiment, CVSS potential of 0 V). Herein,a high level signal is also represented by the value “1”, and a lowlevel signal is also represented by the value “0”.

The first ground line LCS is a conductive line for providing groundpotential CVSS to the memory device 130, and is electrically connectedto the memory device 130 via the ground terminal 210 of the circuitboard 120. The first ground line LCS is a line having a single terminusat the sub-controller 50, and branched termini, corresponding in numberto the number of ink cartridges 100, at the ink cartridge 100. Theground potential CVSS is connected to ground potential VSS (=CVSSpotential) supplied to the sub-controller 50 by the main controller 40via a second ground line LS, and is set to low level (0 V).

The first sensor drive signal line LDSN and the second sensor drivesignal line LDSP are conductive lines adapted to apply a driving voltageto the piezoelectric element of the sensor 110, and after ceasing toapply the driving voltage, transmitting to the sub-controller 50 avoltage produced by the piezoelectric effect of the piezoelectricelement. The first sensor drive signal line LDSN and the second sensordrive signal line LDSP are a plurality of lines that respectively areprovided independently for each ink cartridge 100, and each of which iselectrically connected at a first end to the sub-controller 50 as wellas electrically connected at the other end to the first sensor driveterminal 230 and the second sensor drive terminal 270 of the circuitboard 120, respectively. The first sensor drive signal line LDSN iselectrically connected via the first sensor drive terminal 230 to one ofthe electrodes of the piezoelectric element of the sensor 110, while thesecond sensor drive signal line LDSP is electrically connected via thesecond sensor drive terminal 270 to the other electrode of thepiezoelectric element of the sensor 110.

The first power line LCV is a conductive line for providing the powersupply voltage CVDD, which represents the operating voltage of thememory device 130, to the memory device 130; and is connected to thememory device 130 via the power supply terminal 220 of the circuit board120. The first power line LCV is a line having a single terminus at thesub-controller 50, and branched termini, corresponding in number to thenumber of ink cartridges 100, at the ink cartridge 100. The high levelpower supply voltage CVDD used to drive the memory device 130 usespotential of about 3.3 V versus the low level ground potential CVSS (0V). Of course, depending on factors such as the generation of processorof the memory device 130, the potential level of the power supplyvoltage CVDD may be a different potential, such as 1.5 or 2.0 V forexample.

The main controller 40 and the sub-controller 50 are electricallyconnected by several lines. These several lines include a bus BS, asecond power supply line LV, a second ground line LS, and a third sensordrive signal line LDS. The bus BS is used for data communicationsbetween the main controller 40 and the sub-controller 50. The secondpower supply line LV and the second ground line LS are conductive linesfor providing the main controller 40 and the sub-controller 50 withpower supply voltage VDD and ground potential VSS respectively. Thepower supply voltage VDD uses potential of the same level as the powersupply voltage CVDD provided to the memory device 130 mentionedpreviously, for example, of about 3.3 V versus the ground potential VSSand CVSS (0 V). Of course, depending on factors such as the generationof processor of the logic IC section of the sub-controller 50, thepotential level of the power supply voltage VDD may be a differentpotential, such as 1.5 or 2.0 V for example. The third sensor drivesignal line LDS is a conductive line for providing a sensor drive signalDS (described later) which is ultimately applied to each sensor 110,from the main controller 40 to the sub-controller 50.

The main controller 40 is provided with a control circuit 48, a drivesignal generating circuit 42, and ROM, RAM, EEPROM or the like (notshown). Various programs for controlling the printer 20 are stored inthe ROM.

The control circuit 48 is a CPU (central processing unit), and performscontrol of the printer 20 as a whole in concert with the ROM, RAM,EEPROM or other memory. The control circuit 48 is provided with thefunction blocks of a remaining ink level detection module M1, a memoryaccess module M2, and a ink consumption estimation module M3.

The remaining ink level detection module M1 controls the sub-controller50 and the drive signal generating circuit 42, drives the sensor 110 ofthe ink cartridge 100, and decides whether the ink in the ink cartridge100 equals a prescribed value or greater. Through the sub-controller 50,the memory access module M2 accesses the memory device 130 of the inkcartridge 100 and either reads out the information stored in the memorydevice 130, or updates the information stored in the memory device 130.The ink consumption estimation module M3 is designed to count the dotsthat are jetted onto the printer paper in association with conditions ofprinting operations of the printer 20; and from this count value and theamount of ink consumed by each dot, estimates the amount of ink consumedby printing operations. The amount of ink consumed in head cleaningoperations is estimated as well. On the basis of these estimates, acount is kept of the cumulative estimated value for ink consumptionconsumed from the ink cartridge since the ink cartridge 100 was firstinstalled in the printer 20.

The EEPROM of the main controller 40 stores data representing a sensordrive signal DS for driving the sensor. In accordance with aninstruction from the remaining ink level detection module M1 of thecontrol circuit 48, the drive signal generating circuit 42 reads outfrom the EEPROM data that represents a waveform for the sensor drivesignal DS, and generates a sensor drive signal DS having the desiredwaveform. The sensor drive signal DS includes a potential that isgreater than the power supply voltage CVDD (in the present embodiment,3.3 V); in the present embodiment for example, it includes a maximumpotential of about 36 V. Specifically, the sensor drive signal DS is atrapezoidal pulse signal having maximum voltage of 36 V.

In the present embodiment, the drive signal generating circuit 42 canadditionally generate a head drive signal for presentation to the printhead 5. Specifically, in the present embodiment, during determination ofthe remaining ink amount, the control circuit 48 prompts the drivesignal generating circuit 42 to generate a sensor drive signal, andduring printing operations it prompts the drive signal generatingcircuit 42 to generate a head drive signal.

In terms of hardware configuration, the sub-controller 50 is providedwith an ASIC (Application Specific IC). The ASIC has a communicationprocess module 55 and a sensor process module 52 by way of functionalfeatures.

The communication process module 55 carries out communication processeswith the memory device 130 of each of the ink cartridges 100 via thereset signal line LR1, the data signal line LD1, and the clock signalline LC1. The communication process module 55 also carries outcommunication processes with main controller 40 through the agency ofthe bus BS. By detecting the potentials on prescribed terminals of theterminal group of the circuit board 120, the communication processmodule 55 is able to detect whether the circuit board 120 of an inkcartridge 100 is electrically connected to the printer 20, that is,whether the ink cartridge 100 is installed in the printer 20. Thecommunication process module 55 then notifies the main controller 40that it has detected the installed ink cartridges 100. Through thisprocess the main controller 40 is able to determine whether the inkcartridges 100 are mounted in the cartridge mounting section.

If the main controller 40 determines that the circuit boards 120 areelectrically connected and that the ink cartridges 100 are installed inthe printer 20, it then accesses the memory devices 130 of the installedink cartridges 100 at prescribed timing, via the communication processmodule 55.

The communication process module 55 is a circuit that includes a logiccircuit composed of an ASIC or the like, and that is driven by the powersupply voltage VDD (in the present embodiment, 3.3 V). In the presentembodiment the ASIC is composed of a memory cell area block (SRAM 551)and a logic area, with the logic area being provided with a sensorregister 552 and an error code register 553. The SRAM 551 is a memoryused to temporarily save data during operations of the communicationprocess module 55, i.e. to temporarily save data received from the maincontroller 40, or data received from the sensors 110 or the memorydevices 130, for example. After the printer 20 is powered on, in theSRAM 551 there is allocated memory space sufficient to store datacorresponding to the original data and corresponding to inverted mirrordata of the original data in the memory device 130 of each ink cartridge100 (discussed later); and the data that is read out from the memorydevices is then stored in this allocated memory space. Specifically, inthe memory space in the SRAM 551 there is allocated a memory areasufficient to store the 16-bit original data and the inverted mirrordata of the 16-bit original data, in the same number of rows as thememory cell array of each memory device 130. Then, the original datawhich is read out from the memory array of each memory device, togetherwith the inverted mirror data thereof, is stored in the allocated memoryarea. The values which are read out to the memory area are subsequentlyupdated in association with printing operations (in association withtransmission of write data from the main controller 40 and reading ofdata from the memory devices). Communication errors and memory cellerrors, discussed later, occurring in relation to rows in the rewritablememory area of each memory device 130 are written into the error coderegister 553.

The sensor register 552 is a register used by the sensor process module52 to write process outcomes of sensor processes. A sensor processmodule 552 is provided for each ink cartridge, and is used to recordresults of determination of remaining ink level, discussed later.

The sensor process module 52 executes a remaining ink leveldetermination process using the sensor (sensor process), discussedlater. The sensor process module 52 includes a changeover switch. Thechangeover switch is used to present a sensor drive signal DS suppliedby the drive signal generating circuit 42, to the sensor 110 of a singleink cartridge 100 that is targeted for the sensor process, doing so viaeither the first sensor drive signal line LDSN or the second sensordrive signal line LDSP.

Next, the electrical configuration of the ink cartridges 100 isdescribed. Each ink cartridge 100 has as its electrical elements amemory device 130 and a sensor 110.

The memory device 130 is not designed to accept external input ofaddress data that specifies the address of an access location. Thememory device 130 does not accept direct input of address data; however,it is controllable in order to specify memory cells to be accessed, inresponse to an externally supplied clock signal and command data. Thememory device 130 includes a ferroelectric memory cell array 132provided as the data memory section; and a memory control circuit 136.As indicated by white circles on the broken lines that represent thememory device 130 in FIG. 6, the memory device 130 is provided with aground terminal for electrical connection to the ground terminal 210 ofthe circuit board 120, a power terminal for electrical connection to thepower terminal 220, a reset terminal for electrical connection to thereset terminal 240, and a clock terminal for electrical connection tothe clock terminal 250.

The ferroelectric memory cell array 132 is a nonvolatile semiconductormemory cell array that uses ferroelectric memory elements, and providesa memory area having a data-rewritable feature.

The memory control circuit 136 is designed to control read and writeoperations to the ferroelectric memory cell array 132 in response to thecommand data from the sub-controller 50. The memory control circuit 136analyses identification data and command data sent from thesub-controller 50. Also, during a write operation, on the basis of writecontent data received from the sub-controller 50 the memory controlcircuit 136 generates write data and write it to the ferroelectricmemory cell array 132. Or, during a read operation, on the basis of readdata from the ferroelectric memory cell array 132 the memory controlcircuit 136 generates data for transmission to the sub-controller 50.This will be discussed in detail later.

The memory control circuit 136 is furnished with an ID comparator moduleM11, a command parse module M12, an address counter M13, a read/writecontrol module M14, a data send/receive module M15, a counter controlmodule M16, a copy data generation module M17, an inverted datageneration module M18, and a data determination module M19. The IDcomparator module M11 is designed to compare ID data that is suppliedfrom the sub-controller 50, and the ID number that is assigned to itsown memory device; and to then decide whether the target of access isthe memory device itself. The ID number of the memory device is storedin the memory cells that are connected to the word line which isselected on the basis of the output of the address counter M13 whenaccess from the sub-controller 50 is initiated subsequent toinitialization of the memory device 130. This ID number is used todistinguish a memory device 130 targeted for access by thesub-controller 50, from among the several memory devices 130 which arebus-connected to the sub-controller 50. This ID number may be chosenaccording to the color of the ink contained in the ink cartridge 100,for example. The command parse module M12 is designed to parse Start ofFrame data (SOF), End of Frame (EOF) data, and command data sent fromthe sub-controller 50, and to decide the start of access and end ofaccess from the sub-controller 50, as well as the type of access (read,write, etc.). When a low level reset signal CRST is input to the memorydevice 130 so that the memory device 130 is initialized, the addresscounter M13 resets the counter value. During reset the counter value isset to a value that selects the word line including the memory cells inwhich the ID number is stored. Subsequently, on the basis of controlfrom the counter control module M16, a prescribed number of clock pulsesare sequentially counted from among the clock pulses input to the memorydevice 130. When a memory cell is accessed through control by theread/write control module M14, the counter value of the address counterM13 is output from the address counter M13 to an address decoder of thememory cell array, not shown. Consequently, a prescribed row (word line)of the memory cell array 132 is selected in correspondence with thecounter value. In the present embodiment, a “row” is selected by theaddress decoder on the basis of the counter value output by addresscounter M13. According to the content of the command data (indicative ofthe type of access) that was parsed by the command parse module M12, theread/write control module M14 performs a batch write operation into asingle row and a batch read operation from a single row of theferroelectric memory array 132 that is connected to the word lineselected by the address counter M13. The read/write control module M14is provided with a register, not shown, and is able to temporarily storeoriginal data, inverted data, and mirror data, discussed later indetail. The data send/receive module M15 synchronously with the clocksignal CSCK receives a data signal CSDA sent from the sub-controller 50via the data signal line LD1, or synchronously with the clock signalCSCK sends a data signal CSDA via the data signal line LD1.Specifically, the data send/receive module M15 sets the send/receivedirection of data signals CSDA exchanged between the memory device 130and the sub-controller 50. After initialization, when access to thememory device 130 by the sub-controller 50 is initiated, thesend/receive direction of the data send/receive module M15 is set to thedirection in which the memory device 130 receives data signals CSDA sentfrom the sub-controller 50, so that data read out from the memory cellarray 132 is not sent from the memory device 130 to the sub-controller50. The copy data generation module M17 is adapted to copy original data(discussed later) to generate mirror data (discussed later) equal insize to the original data. The inverted data generation module M18 isadapted to invert the value of each bit of the original data to generateinverted data (discussed later) equal in size to the original data. Thedata determination module M19 is designed to perform a parity check andexclusive OR operation of the original data and the mirror data,discussed later, to determine the consistency of the data. The countercontrol module M16 is furnished with a clock counter. After access tothe memory device 130 by the sub-controller 50 is initiated after thememory device 130 is initialized, the counter control module M16 countsthe number of clock pulses of the clock signal CSCK input to the memorydevice 130. After a prescribed counter value is reached, based on theoutcome of command parsing by the command parse module M12, the countercontrol module M16 issues a control signal to the address counter M13 tocause the address counter M13 to either count up or count down thecounter value. The data send/receive module M15 in the presentembodiment corresponds to the data reception section and the datatransmission section in the present invention.

FIG. 7 is a drawing schematically depicting a memory map of theferroelectric memory array 132 of the memory device 130. In FIG. 7, thememory map of the ferroelectric memory array 132 is composed of multiplerows, each row having 32 cells. The memory cell array 132 is accessedsequentially, in order of row selected by the value indicated by theaddress counter. In the memory map depicted in FIG. 7, the order ofsequential access is from the top to the bottom side, in row units.Here, for convenience, in any given row, memory cells further towardsthe left side (the D31 side) are termed higher order cells. Fordifferent rows, a higher order row than a particular row means a row tothe upper side (a row having a smaller row number) than the particularrow in FIG. 7; and a lower order row than a particular row means a rowto the lower side (a row having a larger row number) than the particularrow in FIG. 7. As shown in the memory map, the memory cell array 132 hasan identification information area, a rewriteable area, a read-onlyarea, and a control area. The identification information area has the32-bit memory area of Row A0, and is used to store the ID numbermentioned earlier. The rewriteable area has a memory area of (m−1) rows,where m is a natural number, from Row A1 to Row Am−1 in FIG. 7. Therewriteable area is an area accessed for the purpose of rewriting databy the sub-controller 50 of the printer 20. The read-only area has amemory area of (n−m) rows from Rows Am to An−1. The read-only area isaccessed for the exclusive purpose of reading data by the sub-controller50 of the printer 20. The control area is provided as a lower order areafrom the read-only area. The control area is a memory area for storingincrement flag information and write lock flag information, discussedlater. Each single row of the storage areas of the memory map of thememory cell array 132 has 32 bit storage capacity. A single rowcorresponds to a row selected by the address counter M13 (i.e. a wordline). Within a single row, the upper 16 bits represent a data area forstoring original data. Here, original data refers to data that is thesource for inverted data and mirror data, discussed later. Herein, thedata area for storing the original data is termed the original dataarea. Within a single row, the lower 16 bits represent a data area forstoring mirror data which is a copy of the original data that is storedon the upper 16 bits. Herein, the data area for storing the mirror datais termed the mirror data area. In FIG. 7, the left half represents theoriginal data area, and the right half represents the mirror data area.Stated the opposite way, in FIG. 7, the data that is stored in theoriginal data area in the left half is original data, and the data thatis stored in the mirror data area in the right half is mirror data.Under normal circumstances, i.e. in the absence of any write errors orfaulty cells in a given row, the original data and the mirror data ineach row have identical content.

In the identification information area and the rewriteable area, theupper 15 bits of the original data area of each row are used for storingactual data; while the last bit (the 16th bit) is used for storingparity data P that is associated with the actual data. In the presentembodiment, actual data is data that is used by the main controller 40of the printer 20 for controlling various aspects of printer 20operation (e.g. printing operations, control of the user interface). Inthe present embodiment, the actual data includes, for example, datarepresenting remaining ink level, the date and time that the inkcartridge was first placed in service, and so on. The upper 15 bits ofthe mirror data area are used for storing mirror data of the actual dataof the original data, while the last bit (the 16th bit) is used forstoring mirror data of the parity data P that is associated with theactual data of the original data. The parity data P is a redundant bitthat is set to a value of either “1” or “0” in such a way that thenumber of bits of “1” value in 16-bit data consisting of the upper 15bits and the parity data P is always an odd number. The parity data Pmay instead be set to either “1” or “0” in such a way that the number ofbits of “1” value in 16-bit data consisting of the upper 15 bits and theparity data P is always an even number. The parity data P should not beconstrued as limiting, and any of various of types of redundancy datathat provide redundancy of actual data may be used instead.

Of the (n−m) rows in the read-only area, rows except for the last rowAn−1 are used for actual data storage, while the last row is used forparity data storage. Specifically, for each of prescribed units ofactual data (e.g. 8-bit or 16-bit units) of rows except for the lastrow, 1-bit parity data is assigned to a bit in the last row. In FIG. 7,the cells denoted by “P” represent 1-bit memory areas for storing paritydata P.

As will be appreciated from the preceding discussion, in theidentification information area and the rewriteable area, the originaldata consists of actual data and parity data. In the read-only area, inareas apart from the last row, the original data is actual data per se.In the read-only area, in the last row, the original data is paritydata.

The rewriteable area stores various kinds of information, for example,remaining ink level information or usage history information for the inkcartridge 100. The ID number (identification information, which ischosen for each type (color) of ink cartridge 100, is stored on the 8bits starting from the lead cell in the leading first row (theidentification information area of Row A0) which is selected by theinitial value of the address counter M13 immediately after access to thememory device 130 is initiated. In FIG. 7, the area storing the IDnumber is indicated by fine hatching. The remaining cells of Row A0,i.e. excepting the original data parity bit cells and the cells storingthe ID number, constitute empty areas and store fixed data of 0 or 1.For example, where the number of ink cartridges 100 installed in theprinter 20 is n, the ID number may assume n types of values that differaccording to the type of ink cartridge 100. The first row of therewriteable area (Row A1) stores a first ink consumption count value X(e.g. on 10 bits), and the second row (Row A2) stores a second inkconsumption count value Y (e.g. on 10 bits). The first ink consumptioncount value X represents 10-bit information for example, and is storedin the cells of the lower 10 bits among 15 bits excepting the parityinformation cell of Row A1. The remaining 5 bits of Row A1 constitute anempty area storing fixed data, and data is sent from the printer 20 sothat “1”s are always stored therein. In FIG. 7, the area storing thefirst ink consumption count value X is indicated by coarse hatching. Thesecond ink consumption count value Y represents 10-bit information forexample, and is stored in the cells of the lower 10 bits among 15 bitsexcepting the parity information cell of Row A2. The remaining 5 bits ofRow A2 constitute an empty area, and data is sent from the printer 20 sothat “1”s are always stored therein. In FIG. 7, the area storing thesecond ink consumption count value Y is indicated by crosshatching. Thefirst ink consumption count value X and the second ink consumption countvalue Y are values that represent cumulative total ink consumption foreach ink cartridge 100, derived on the basis of the ink consumption thatwas estimated by the ink consumption estimation module M3 in the printer20. Ink end information M is also stored in a prescribed row of therewritable area. The ink end information M may be 2-bit data thatassumes one of three states “01”, “11” or “01” for example. “01”represents a state in which the sensor 110 of the ink cartridge 100 hasnot detected that the remaining ink level is equal to or less than afirst threshold value Vref1 (hereinafter also referred to as the fullstate), that is, that the remaining ink level is greater than the firstthreshold value Vref1. “10” represents a remaining ink level equal to orless than the first threshold value Vref1 and greater than the ink endlevel (hereinafter also referred to as the low state; that is, firstthreshold value Vref1>ink end level. The fact that the remaining inklevel is equal to or less than the first threshold value Vref1 isdetected by the sensor 110 of the ink cartridge 100 in question. “11”represents a remaining ink level at or below the ink end level(hereinafter also referred to as the end state). The ink end level is alevel of remaining ink at which, if the printer 20 continues to printuninterrupted, poses a risk of air becoming incorporated into the printhead unit 60 due to ink depletion, thus making it imperative to replacethe ink cartridge 100. For example, the first threshold value Vref1 maybe set to about 1.5 grams, and the ink end level may be set to aremaining ink level of about 0.8 grams. Processes relating to the firstink consumption count value X, the second ink consumption count value Y,and the ink end information M will be discussed later.

The read-only area stores, for example, manufacturer informationindicating the manufacturer of the ink cartridge 100, the date ofmanufacture of the ink cartridge, the ink cartridge 100 capacity, thetype of ink cartridge, and so on. The control area stores increment flaginformation and write lock information.

One bit of increment flag information is provided for each row on thememory map. A row whose associated increment flag information is set to“1” represents an area in which the row is allowed to be overwrittenwith only a larger numerical value than the numerical value alreadystored in the row (incremental overwrite), but the row is not allowed tobe overwritten with a smaller numerical value than the numerical valuealready stored in the row (decremental overwrite). A row whoseassociated increment flag information is set to “0” is allowed to beoverwritten freely. The decision as to whether to allow only incrementaloverwrites or to allow free overwriting is made by the read/writecontrol module M14 of the memory control circuit 136, with reference tothe increment flag information. Specifically, for Row A1 and Row A2which record the aforementioned first ink consumption count value X andsecond ink consumption count value Y, the corresponding increment flaginformation is set to “1”. The reason is that it is difficult to imaginethat updating of first ink consumption count value X and the second inkconsumption count value Y by the printer 20 would take place in anythingother than the increasing direction. This can reduce the likelihood ofwrite errors to Row A1 and Row A2. Hereinbelow, memory areas for which,like Row A1 and Row A2, the corresponding increment flag information isset to “1” is also referred to as increment areas. Overwriting to a rowmay be allowed in instances where the data overwrite is an incrementaloverwrite made in 16-bit original data units rather than in row units.Where remaining ink level, rather than ink consumption, is saved in arow of the memory, this row may be controlled by a flag value thatindicates whether to allow only decremental overwriting or to allow freeoverwriting.

One bit of write lock flag information is provided for each row in theidentification information area, the rewriteable area, and the read-onlyarea. A row whose associated write lock flag information is set to “1”represents an area that is not allowed to be overwritten throughexternal access. A row whose associated write lock flag information isset to “0” represents an area that is allowed to be overwritten throughexternal access. The decision as to whether to allow overwriting is madeby the read/write control module M14 of the memory control circuit 136,with reference to the write lock flag information. For the rewriteablearea, i.e. Rows A1 to Am−1, the corresponding write lock flaginformation is set to “0” at the factory prior to shipping, so as topermit erasing and/or rewriting of data by the communication processmodule 55 of the printer 20. On the other hand, for the identificationinformation area, i.e. Row A0, and for the read-only area, i.e. Rows Amto An−1, the corresponding write lock flag information is set to “1” atthe factory prior to shipping, so as to prohibit erasing and/orrewriting of data by the communication process module 55 of the printer20. Such memory areas for which the write lock flag information is setto “1” is also referred to as write-locked areas.

The sensor 110, which is not depicted in detail in the drawings, isfurnished with a cavity (resonance portion) that defines part of the inkflow channel in proximity to the ink delivery section; an oscillatorplate forming part of the wall of the cavity; and a piezoelectricelement arranged on the oscillator plate. The sensor process module 52of the printer 20 can apply a sensor drive signal DS to thepiezoelectric element via the sensor drive terminals 230, 270, andthereby induce oscillation of the oscillator plate through the agency ofthe piezoelectric element. Then, by receiving from the piezoelectricelement a response signal RS having the frequency of the residualvibration of the oscillator plate, the sensor process module 52 candetect if ink is present or absent in the cavity. Specifically, if theink contained in the main body 101 is consumed so that the condition ofthe cavity interior changes from a condition filled with ink to acondition filled with air, the frequency of the residual vibration ofthe oscillator plate changes. This change in frequency is reflected in achange in frequency of the response signal RS. By measuring thefrequency of the response signal RS, the sensor process module 52 candetect if ink is present or absent in the cavity. Detecting that ink is“absent” in the cavity means that the remaining ink level contained inthe main body 101 is equal to or less than the first threshold valueVref1 (this corresponds to the amount of ink remaining downstream fromthe cavity). Detecting that ink is “present” in the cavity means thatthe remaining ink level contained in the main body 101 is greater thanthe first threshold value Vref1.

Read Operation from Memory Device:

FIG. 8 is a flowchart depicting the processing routine of a readoperation from the memory device 130, executed by the sub-controller 50of the printer 20. FIG. 9 is a timing chart schematically depictingsignals exchanged between the communication process module 55 of theprinter 20 and the memory control circuit 136 of the memory device 130during a read operation from the memory device 130. In FIG. 9, anexample of a power supply voltage CVDD, a reset signal CRST, a clocksignal CSCK, and a data signal CSDA is depicted. The power supplyvoltage CVDD is a signal that appears on the first power supply line LCVconnecting the sub-controller 50 and the memory device 130, and issupplied to the memory device 130 by the sub-controller 50. The resetsignal CRST is a signal that appears on the reset signal line LR1connecting the sub-controller 50 and the memory device 130, and issupplied to the memory device 130 by the sub-controller 50. The clocksignal CSCK is a signal that appears on the clock signal line LC1connecting the sub-controller 50 and the memory device 130, and issupplied to the memory device 130 by the sub-controller 50. The datasignal CSDA is a signal that appears on the data signal line LD1connecting the sub-controller 50 and the memory device 130. In FIG. 9,the data direction of the data signal CSDA is indicated as well. Therightward pointing arrows represent the direction in which thesub-controller 50 is at the sending side and the memory device 130 is atthe receiving side. The leftward pointing arrows represent the directionin which the sub-controller 50 is at the receiving side and the memorydevice 130 is at the sending side. In the present embodiment, the memorydevice 130 sends and receives data synchronously with the rise of theclock signal CSCK presented to it by the sub-controller 50. Sending andreceiving of data takes place when the clock signal CSCK rises and thelevel of the data signal on the data terminal of the memory device 130has a valid value for sending or receiving of data. FIG. 10 is aflowchart schematically depicting the processing routine an operationexecuted by the memory control circuit 136 on the memory side.

The main controller 40 of the printer 20, via the bus BS, sends thesub-controller 50 a Read command instructing that a read operation fromthe memory device 130 of the ink cartridge 100 be carried out. Thecommunication process module 55 supplies the power supply voltage CVDDto each of the ink cartridges 100 via the first power supply line LCV.Specifically, the memory device 130 of each of the ink cartridges 100 issupplied with operating voltage, thereby placing the memory device 130in the operational state. After supplying the power supply voltage CVDD,a low level reset signal is supplied to initialize the memory devices130. Because the reset signal remains at low level since the time thatthe previous access ended, it is at low level even before the powersupply voltage CVDD is supplied to the memory device 130. When thecommunication process module 55 of the sub-controller 50 receives theRead command, the read operation depicted in the flowchart of FIG. 8starts.

When the read operation starts, the communication process module 55transitions the reset signal CRST from low level to high level, andtransmits a clock signal CSCK of prescribed frequency (FIG. 9). When thereset signal CRST rises from low level to high level, the memory device130 goes into a standby state to accept a data signal CSDA from thecommunication process module 55.

The communication process module 55 first transmits SOF (Start Of Frame)data as a data signal CSDA (FIG. 8: Step S102, FIG. 9). The SOF data isan 8-bit data signal having a prescribed waveform, and transmitted insync with the clock signal CSCK. The purpose of transmitting the SOF isto notify the memory device 130 of the start of communication.

Following the SOF data, the communication process module 55 sends anoperation code. An operation code is a sequence of identification dataand command data. Command data is data for indicating a particular typeof access (e.g. a read or write operation) to the memory device 130. Thecommunication process module 55 sends identification data as a datasignal CSDA (FIG. 8: Step S104). The identification data isidentification information that specifies the memory device 130 of anink cartridge 100 that is targeted for a read operation, and includesidentification data of 8 bits and inverted identification data of 8 bits(FIG. 9). Here, the inverted data is data of the same size (same numberof bits) as the original data, but in the data the value of each bit ofthe original data is inverted. For example, if an m-th value (m is anatural number) of the original data is a “1”, in the inverted data, them-th value becomes a “0”; and if an m-th value of the original data is a“0”, in the inverted data, the m-th value becomes a “1”. Hereinbelowwhere original data is denoted by the symbol A, the inverted datathereof is denoted by a preceding/(slash symbol), i.e. /A. For example,for original data A=(01001001), the inverted data /A=(10110110). Theinverted identification data is generated by the main controller 40 orthe communication process module 55 on the basis of the identificationdata. By duplicating the identification data in this way, unintendedoperation of the memory device 130 of an ink cartridge 100 not targetedfor operation may be avoided.

Following the identification data, the communication process module 55sends command data as a data signal CSDA (FIG. 8: Step S106). Commanddata includes original command data of 8 bits and inverted command dataof 8 bits (FIG. 9). Here, because the operation is a read operation fromthe memory device 130 to the sub-controller 50, the command data sent inthe operation is a command indicating a read operation (Read command).In the original command data CM, of the 8 bits, the upper 4 bits and thelower 4 bits have an inverted relationship to each other. For example,if the upper 4 bits of the original command data CM are “0110” the lower4 bits of the original command data CM are “1001”, and the invertedcommand data /CM are “10010110”. The inverted command data are generatedby the main controller 40 or the communication process module 55 on thebasis of the original command data. By providing such redundancy ofcommand data, erroneous operation of the memory device 130 can beavoided.

In synchronization with the next rise of the clock signal CSCK followingthe end of transmission of the command data, reception of the read datasent from the memory device 130 starts. The communication process module55 receives read data including data that is read out from a row of thememory device 130. To discuss in more detail, the communication processmodule 55 receives a unit of read data equivalent to 8 bits×8=64 bits,doing so sequentially one bit at a time in sync with rise of the clocksignal CSCK (FIG. 8: Step S108, FIG. 9). The 64-bit unit of read dataconsist of original data upper 8 bits UDn (n is a natural number);inverted original data upper 8 bits /UDn representing inverted data ofthe original data upper 8 bits UDn; original data lower 8 bits LDn;inverted original data lower 8 bits /LDn representing inverted data ofthe original data lower 8 bits LDn; mirror data upper 8 bits Udnrepresenting mirror data of the original data upper 8 bits UDn; invertedmirror data upper 8 bits /Udn representing inverted original data upper8 bits Udn; mirror data lower 8 bits Ldn representing mirror data of theoriginal data lower 8 bits LDn; and inverted mirror data lower 8 bits/Ldn representing inverted original data lower 8 bits Ldn (FIG. 9).

The 16-bit data having the original data upper 8 bits UDn as its upperbits and the original data lower 8 bits LDn as its lower bits are alsoreferred to as original data Dn. The 16-bit data having the invertedoriginal data upper 8 bits /UDn as its upper bits and the invertedoriginal data lower 8 bits /LDn as its lower bits are also referred toas inverted data /Dn. The 16-bit data having the mirror data upper 8bits Udn as its upper bits and the mirror data lower 8 bits Ldn as itslower bits are also referred to as mirror data dn. The 16-bit datahaving the inverted mirror data upper 8 bits /Udn as its upper bits andthe inverted mirror data lower 8 bits /Ldn as its lower bits are alsoreferred to as inverted mirror data /dn. That is, the unit of read datacan be said to represent data made up of original data Dn, inverted data/Dn, mirror data dn, and inverted mirror data /dn. Ultimately, byrepeating reception of units of read data n times, the communicationprocess module 55 of the sub-controller 50 receives all of the data thatis to be read (discussed later). It should be noted that the originaldata Dn and mirror data dn are read out from the memory cell array 132while the inverted data /Dn and inverted mirror data /dn are generatedfrom the original data Dn and mirror data dn by the inverted datageneration module M18.

When a unit of read data is received, the communication process module55 temporarily stores the unit of read data in a register (not shown)and executes the process described below. First, from the unit of readdata, the communication process module 55 decides whether or not theexclusive OR of an m-th value of the original data Dn and an m-th valueof the inverted mirror data /dn is true “1” for all values of m (1≦m≦16)(FIG. 8: Step S110). In general, the output of an exclusive OR circuitis true “1” if the two inputs have different values, and is false “0” ifthe two inputs have an identical value. If the output of the exclusiveOR operation is true for all 16 bits, i.e. if 1111111111111111=FFFF inhexadecimal notation (FIG. 8: Step S110: YES), the communication processmodule 55 decides that the communication status and the memory cellsthat have been read are normal, and stores the original data Dn and theinverted mirror data /dn in an allocated memory area (discussed above)of the SRAM 551 (FIG. 8: Step S120).

If on the other hand the output of the exclusive OR operation is false“0” for any of the 16 bits, i.e. if not FFFF (FIG. 8: Step S110: NO),the communication process module 55 decides whether or not the exclusiveOR of an m-th value of the original data Dn and an m-th value of theinverted data /Dn is true “1” for all values of m (1≦m≦16) (FIG. 8: StepS112). If the output of the exclusive OR operation is FFFF (FIG. 8: StepS112: YES), the communication process module 55 decides whether or notthe exclusive OR of an m-th value of the mirror data dn and an m-thvalue of the inverted mirror data /dn is true “1”, for all values of m(1≦m≦16) (Step S114). If the exclusive OR operation outcomes for all them-th values of the original data Dn and all the m-th values of theinverted data /Dn are not FFFF (FIG. 8: Step S112: NO), or if theexclusive OR outcomes for all the m-th values of the mirror data dn andall the m-th values of the inverted mirror data /dn are not FFFF (FIG.8: Step S114: NO), the communication process module 55 decides thatthere is a communication error, and stores the original data Dn and theinverted mirror data /dn to a memory area allocated in the SRAM 551, aswell as saving a prescribed communication error code indicating thecommunication error to the error code register 553 in the communicationprocess module 55 (FIG. 8: Step S118), then carry out a prescribed errorprocess (Step S124) and terminate the read operation. The error coderegister 553 may also store included information indicating whether thecommunication error occurred in communication of the original data fromthe memory device (corresponds to NO in S112) or whether thecommunication error occurred in communication of the mirror data fromthe memory device (corresponds to NO in S114). The prescribed errorprocess may involve notifying the main controller 40 of thecommunication error, or that the read operation is ceased, for example.The prescribed error process may also be omitted. By referring to thecommunication error code stored in the SRAM 551, the main controller 40acknowledges the occurrence of a communication error. If the maincontroller 40 further acknowledges whether the communication error isoccurred in the original data or the mirror data, the data in which nocommunication error is occurred may be utilized for processes executedby the main controller 40.

If the exclusive OR operation outcomes for all the m-th values of theoriginal data Dn and all the m-th values of the inverted data /Dn areFFFF (FIG. 8: Step S112: YES), and if the exclusive OR outcomes for allthe m-th values of the mirror data dn and all the m-th values of theinverted mirror data /dn are FFFF (FIG. 8: Step S114: YES), there is ahigh probability that the data that was stored in the original data areaof the memory device 130 and that the data that was stored in the mirrordata area do not have consistency; therefore, the communication processmodule 55 decides that a memory cell error is occurred in the memorydevice 130, and then stores the original data Dn and the inverted mirrordata /dn to an allocated memory area in the SRAM 551, as well as savinga prescribed communication error code indicating the cell error to theerror code register 553 in the communication process module 55 (FIG. 8:Step S116). A cell error is a problem whereby, in either a memory cellstoring original data targeted for the operation or a memory cellstoring mirror data targeted for the operation, the memory cell per sebecomes damaged so that the saved information can no longer be savedcorrectly.

Once Step S120 or Step S116 is executed, the communication processmodule 55 decides whether all data targeted for the read operation areread out (FIG. 8: Step S122). If all of the data to be read are read(FIG. 8: Step S122: YES), the communication process module 55 terminatesthe read operation. Once the communication process module 55 terminatesthe read operation as depicted in FIG. 9, it transits the reset signalCRST from high level to low level, and ceases to supply the clock signalCSCK. Once the communication process module 55 ceases to supply theclock signal CSCK, it then ceases to supply the power supply voltageCVDD. If not all of the data to be read are read yet (FIG. 8: Step S122:NO), the communication process module 55 returns to Step S108 andrepeats the process discussed above for the next unit of read data. Forexample, once the above process is carried out for the first unit ofread data D1, /D1, d1, /d1, the above process is then carried out forthe second unit of read data D2, /D2, d2, /d2. In the presentembodiment, once reading of Row A1 is complete, reading of Row A2 takesplace. Read operations are repeated until the information in the rowsstoring the information that the main controller 40 intends to read isread out.

The discussion now turns to processing that takes place on the memorydevice 130 (memory device processing) in response to a read operationfrom the memory device 130 at the communication process module 55discussed above. Because processing executed in the memory device 130 isthe same up to step of receiving the operation code and step of parsingthe command data (type of access), the discussion is not limited to readoperations and includes other processes (e.g. write operations) as well.The memory device 130 receives input of power supply voltage CVDD fromthe sub-controller 50 and is activated. The memory device 130 theninitializes itself in response to input of a low level reset signalCRST. After receiving supply of power supply voltage CVDD, because thereset signal CRST is low (FIG. 9), the memory device 130 goes into theinitialized state and initiates memory device side processing.

After initialization of the memory device 130 is carried out, theaddress counter M13 is set to its initial value at the time ofinitialization, and the various registers are reset to their initialvalues as well. Additionally, the data send/receive module M15 of thememory device 130 sets the send/receive direction for data exchanged viathe data terminal to the direction in which the memory device 130receives data from the sub-controller 50. The read/write control moduleM14 sets the data transfer direction vis-à-vis the ferroelectric memoryarray 132 to the data read direction.

As depicted in FIG. 10, once processing is initiated on the memorydevice, the memory control circuit 136 of the memory device 130 receivesSOF data as a data signal CSDA (FIG. 10: Step S210). Following the SOFdata, the memory control circuit 136 receives identification data (FIG.10: Step S210). Once the identification data is received, the IDcomparator module M11 determines whether the received identificationdata is correct (Step S225). Specifically, for the identification dataand the inverted identification data included in the receivedidentification data, the ID comparator module M11 takes the exclusive ORone bit at a time, and determine whether all output values of theexclusive OR are 1's. That is, it determines whether there are anycommunication errors in the received identification data. If there areno communication errors, the received identification data is deemed tobe correct, whereas if communication errors are found, the receivedidentification data is deemed to be not correct. In the event that theID comparator module M11 decides that the received identification datais not correct (FIG. 10: Step S225: NO), it terminates with no furtherprocessing.

If on the other hand the ID comparator module M11 decides that thereceived identification data is correct (Step S225: YES), it thendecides whether the ID number (identification information) that isassigned to the memory device 130 itself matches the receivedidentification data (FIG. 10: Step S230). At this time, because theaddress counter M13 is currently selecting Row A0 by the initialization,the read/write control module M14 reads out the ID number(identification information) that is stored in Row A0. The ID comparatormodule M11 then accepts the ID number (identification information) thatis assigned to the memory device in the first row (FIG. 7: Row A0) ofthe memory area read out by the read/write control module M14, andcompares bit for bit the ID number (identification information) assignedto the memory device with the identification data contained in theidentification data that has been sent from the communication processmodule 55. If the ID number (identification information) assigned to thememory device and the received identification data do not match, the IDcomparator module M11 decides that the ID number (identificationinformation) assigned to the memory device and the receivedidentification data do not match.

If the ID comparator module M11 decides that the ID number(identification information) assigned to the memory device does notmatch the received identification data (FIG. 10: Step S230: NO), thememory control circuit 136 terminates with no further processing. If theID comparator module M11 decides that the ID number (identificationinformation) assigned to the memory device matches the receivedidentification data (FIG. 10: Step S230: YES), the memory controlcircuit 136 receives the command data that is transmitted as a datasignal CSDA subsequent to the identification data (FIG. 10: Step S240).Once the command data is received, the command parse module M12 of thememory control circuit 136 first determines whether the received commanddata is correct (Step S245). Specifically, the command parse module M12decides whether the upper 4 bits and the lower 4 bits of the originalcommand data contained in the received command data are inverted data ofone another. The command parse module M12 additionally decides whetherthe upper 4 bits and the lower 4 bits of the inverted command datacontained in the received command data are inverted data of one another.The command parse module M12 also takes the exclusive OR one bit at atime for the original command data and the inverted command data, anddecide whether or not all output values of the exclusive OR are 1's. Ifthe upper 4 bits and the lower 4 bits of the original command datacontained in the received command data are found to be inverted data ofone another, the upper 4 bits and the lower 4 bits of the invertedcommand data contained in the received command data are found to beinverted data of one another, and an exclusive OR result of 1 isobtained for all bits of the original command data and the invertedcommand data, the command parse module M12 decides that the receivedcommand data is correct (devoid of communication errors). If on theother hand the upper 4 bits and the lower 4 bits of the original commanddata contained in the received command data are not found to be inverteddata of one another, or the upper 4 bits and the lower 4 bits of theinverted command data contained in the received command data are notfound to be inverted data of one another, or the exclusive OR result isnot 1 for any bit of the original command data and the inverted commanddata, the command parse module M12 decides that the received commanddata is not correct (contains communication errors).

In the event of a decision that the command data is not correct (StepS245: NO), the memory control circuit 136 terminates processing. If onthe other hand it is decided that command data is correct (Step S245:YES), the command parse module M12 of the memory control circuit 136parses the received command and determine the type of access (FIG. 10:Step S250). Here, possible types of command data includes at least aWrite command, a Read command, and a Write Lock command. A Write commandis a command instructing that data be written into the ferroelectricmemory array 132. A Read command is a command instructing that data beread from the ferroelectric memory array 132. A Write Lock command is acommand instructing that of a write lock operation, discussed later, beexecuted on the memory device; the command instructs that a Write Lockflag, indicating that a specified row of the ferroelectric memory cellarray 132 is a write-prohibited row, be written into the control area,in order to prohibit write operations to the row from the communicationprocess module 55.

If the command directed to the memory device 130 does not correspond toany of the above types of command, the command parse module M12 decidesthat the command data is not parsable. If the command parse module M12decides that the command data is not parsable, the memory controlcircuit 136 proceeds to terminate, and do nothing (not shown).

If the command parse module M12 decides that the command indicated bythe command data is a Read command, the memory control circuit 136executes a read operation on the memory device (FIG. 10: Step S260). Ifthe command parse module M12 decides that the command indicated by thecommand data is a Write command, the memory control circuit 136 executesa write operation on the memory device (FIG. 10: Step S280). If thecommand parse module M12 decides that the command indicated by thecommand data is a Write Lock command, the memory control circuit 136executes a write lock operation on the memory device (FIG. 10: StepS270). If a read operation on the printer 20 depicted in FIG. 8 is beingcarried out by the communication process module 55, the memory controlcircuit 136 receives a Read command as command data; and as long as nocommunication error is occurred, the command parse module M12 decidesthat the command indicated by the command data is a Read command, andthe memory control circuit 136 executes the read operation on the memorydevice. The steps of the flowchart depicted in FIG. 10 may be executedin a different order or in parallel, as long as no conflicts occurs inthe process. For example, the memory control circuit 136 may decide ifthe identification data is correct after confirming a match between theidentification data stored in the memory device and the identificationdata supplied from the communication process module 55; or it may decideif the identification data is correct while receiving the command datain a parallel process.

FIG. 11 is a flowchart depicting the processing routine of a readoperation (FIG. 10: Step S260) on the memory device. The read/writecontrol module M14 of the memory control circuit 136 reads data from theferroelectric memory cell array 132 according to the address that isselected by the output of the address counter M13, and send it as a datasignal CSDA to the communication process module 55. After the operationcode is received, if the command indicated by the command data is a Readcommand, the data send/receive module M15 sets the send/receivedirection of data to be exchanged via the data terminal to the directionof sending data from the memory device 130 to the sub-controller 50.Moreover, if the command indicated by the command data is a readcommand, the counter control module M16 supplies a control signal to theaddress counter M13 specifying Row A1 as the initial row targeted forreading. Then, based on the address specified by the count value of theaddress counter M13, the read/write control module M14 reads out datainto a register, not shown, from the ferroelectric memory array 132 in1-row (32-bit) increments (FIG. 11: Step S2602). The first row to beread out is Row A1 shown in FIG. 7.

From the 32 bits that were read into the register, the data send/receivemodule M15 first selects the upper 8 bits as the original data upper 8bits UDn mentioned previously, and sends these to the sub-controller 50(FIG. 11: Step S2604). Next, the inverted data generation module M18inverts each bit of the original data upper 8 bits UDn to generateinverted original data upper 8 bits /UDn. The data send/receive moduleM15 then sends the generated inverted original data upper 8 bits /UDn tothe sub-controller 50 (FIG. 11: Step S2606). Next, from the 32 bits thatwere read into the register, the data send/receive module M15 selectsthe 8 bits from the 9th to 16th bits as the original data lower 8 bitsLDn mentioned previously, and sends these to the sub-controller 50 (FIG.11: Step S2608). Then, the inverted data generation module M18 invertseach bit of the original data lower 8 bits LDn to generate invertedoriginal data lower 8 bits /LDn. The data send/receive module M15 thensends the generated inverted original data lower 8 bits /LDn to thesub-controller 50 (FIG. 11: Step S2610). Next, from the 32 bits thatwere read into the register, the data send/receive module M15 selectsthe 8 bits from the 17th to 24th bits as the mirror data upper 8 bitsUdn mentioned previously, and sends these to the sub-controller 50 (FIG.11: Step S2612). Then, the inverted data generation module M18 invertseach bit of the mirror data upper 8 bits Udn to generate inverted mirrordata upper 8 bits /Udn. The data send/receive module M15 then sends thegenerated inverted mirror data upper 8 bits /Udn to the sub-controller50 (FIG. 11: Step S2614). Next, from the 32 bits that were read into theregister, the data send/receive module M15 selects the 8 bits from the25th to 32nd bits as the mirror data lower 8 bits Ldn mentionedpreviously, and sends these to the sub-controller 50 (FIG. 11: StepS2616). Then, the inverted data generation module M18 inverts each bitof the mirror data lower 8 bits Ldn to generate inverted mirror datalower 8 bits /Ldn. The data send/receive module M15 then sends thegenerated inverted mirror data lower 8 bits /Ldn to the sub-controller50 (FIG. 11: Step S2618).

After sending of the 32 bits that are read into the register isfinished, if transmission of all of the data that is requested to beread by the sub-controller 50 is not completed (FIG. 11: Step S2620:NO), the memory control circuit 136 returns to Step S2602, and repeatsthe process of Steps S2602 to S2618 for the data of the next row (32bits) of the ferroelectric memory array 132. Once transmission of all ofthe data is completed, the memory control circuit 136 terminates theprocess.

In the event that the ID comparator module M11 or the command parsemodule M12 determines that the ID data or the command data CM includes acommunication error, and the memory control circuit 136 terminatesprocessing without any meaningful process accordingly, the memory device130 does not transmit any data during the read data transmission period.As described previously, the data signal line LD1 is maintained at a lowlevel by the resistor R1 of the sub-controller 50 when there is no datatransmission between the sub-controller 50 and the memory device 130.Then the communication process module 55 receives low level data duringthe entire period for receiving the original data Dn and the inverteddata /Dn, whereby the decision of Step S112 in FIG. 8 is NO, and thecommunication process module 55 decides that a communication error isoccurred. Through the read operation described above, original data Dnand inverted mirror data /dn are stored in the SRAM 551. If an error isoccurred, a communication or cell error code is stored in the error coderegister 553 of the communication process module 55. The original dataDn and inverted mirror data /dn, as well as any communication or cellerror code, stored in the communication process module 55 are retrievedby the main controller 40. For original data Dn and inverted mirror data/dn with no associated error code, the main controller 40 uses theoriginal data Dn to carry out a prescribed control process (e.g.checking the remaining ink level or notifying the user of the remainingink level). In the case of original data Dn and inverted mirror data /dnwith an associated communication error code, the main controller 40performs a communication error response process, for example, displayingon the display panel of the console portion 70 a message prompting theuser to recheck installation of the ink cartridge 100. Or, in the caseof original data Dn and inverted mirror data /dn having an associatedcell error code, the main controller 40 performs a parity check of theoriginal data Dn and the inverted mirror data /dn, respectively, forwhich the cell error is diagnosed. As noted above, the original data Dnand the inverted mirror data /dn include actual data and parity data(FIG. 7). The main controller 40 selects the data, from the originaldata Dn and the inverted data /dn with the associated cell error, inwhich the 15 bits of actual data and the 1 bit of parity data haveconsistency, and uses it to carry out a prescribed control process. Ifas a result of the parity check of the original data Dn and invertedmirror data /dn with the associated cell error, both the original dataDn and inverted mirror data /dn are found to have a parity error, or ifboth have parity consistency, a message alerting the user of an inkcartridge 100 memory error is displayed on the display panel of theconsole portion 70. Also, where readout from the memory device 130 iscarried out for the purpose of verifying the write result of datawritten into the memory device 130, the write data which is kept by themain controller 40 may be compared with the original data Dn andinverted mirror data /dn having the associated cell error, to determinewhether the data is correct. In the present embodiment, in Step S2602,data stored in one row is read out from the memory cell array 132, butreadout of data from the memory cell array 132 need not take place in1-row units, provided that subsequent to reception of the command data,data can be sent in sync with the clock signal provided to the memorydevice 130, in order from Step S2604 to Step S2618.

Write Operation to Memory Device:

FIG. 12 is a flowchart depicting the processing routine of a writeoperation to the memory device 130, executed by the sub-controller 50 onthe printer 20. FIG. 13 is a drawing schematically depicting a memorymap of the memory device 130 recognized by the main controller 40 on theprinter 20 during a write operation to the memory device 130. FIG. 14 isa timing chart schematically depicting signals exchanged between thecommunication process module 55 of the printer 20 and the memory controlcircuit 136 of the memory device 130 during a write operation to thememory device 130. In FIG. 14, as in FIG. 9, the power supply voltageCVDD, the reset signal CRST, the clock signal CSCK, the data signalCSDA, and the data direction are shown. FIG. 15 is a flowchart depictingthe processing routine of a write operation executed by the memorycontrol circuit 136 of the memory device 130.

Via the bus BS, the main controller 40 of the printer 20 writes to theSRAM 551 in the sub-controller 50, the data that is to be written intothe memory device 130 of a particular ink cartridge 100. Specifically,this data is written into write target rows which are allocated in theSRAM 551 for writing of original data corresponding to the ferroelectricmemory cell array 132 of the memory device 130. During a writeoperation, the main controller 40 recognizes that the memory device 130is a memory in which one row equals 16 bits. Thus, the data that is tobe written into the memory device 130 is divided into 16-bit units, inwhich 16-bit unit the upper 15 bits are actual data and the lower 1 bitis parity data. The parity data may also be generated by the maincontroller 40, appended to the upper 15 bit actual data, and writteninto the SRAM 551 as data of 16 bits in total. Alternatively, the paritydata may also be generated by the sub-controller 50, and appended eachtime that 15-bit data is written into the SRAM 551 by the maincontroller 40. The main controller 40 then transmits to thesub-controller 50 via the bus a Write command instructing that thewrite-targeted memory device 130 be notified, and that the data that iswritten into the SRAM 551 be written into the memory device 130 that istargeted for the write operation. Upon receiving the Write command, thesub-controller 50 supplies each ink cartridge 100 with the power supplyvoltage CVDD via the first power supply line LCV, placing the memorydevice 130 of each ink cartridge 100 in the operable state. After thepower supply voltage CVDD is supplied by the sub-controller 50, a lowlevel reset signal CRST is supplied by the sub-controller 50 and thememory devices 130 is initialized. Because the reset signal remains atlow level since the time that the previous access ended, it is at lowlevel even before the power supply voltage CVDD is supplied to thememory devices 130. The communication process module 55 of thesub-controller 50 then initiates the write operation shown in theflowchart of FIG. 12.

During write operations, the communication process module 55 recognizesthe memory map depicted in FIG. 13 as the memory map of the memorydevice 130. That is, during write operations, in the actual memory mapcorresponding to the actual ferroelectric memory array (FIG. 7), thecommunication process module 55 recognizes only the presence of theblock storing the original data (the left hand block in FIG. 7), anddoes not recognize the presence of the block storing mirror data. Thecommunication process module 55 recognizes that multiple rows eachconsisting of a memory area containing 16 bits per row are arrayed inthe block storing the original data.

When the write operation starts, the communication process module 55transitions the reset signal CRST from low level to high level, andtransmits a clock signal CSCK of a prescribed frequency (FIG. 14). Whenthe reset signal CRST rises from low level to high level, the memorycontrol circuit 136 of the memory device 130 goes into a standby stateto accept a data signal CSDA from the communication process module 55.

As in the read operation described earlier, the communication processmodule 55 first transmits SOF data as a data signal CSDA (FIG. 12: StepS302, FIG. 14). As in the read operation described earlier, followingthe SOF data, the communication process module 55 sends identificationdata as a data signal CSDA (FIG. 12: Step S304, FIG. 14). Following theidentification data, the communication process module 55 sends commanddata as a data signal CSDA (FIG. 14: Step S306, FIG. 14). The commanddata sent in the present operation is a Write command indicating a writeoperation.

In sync with the next rise of the clock signal CSCK following the end oftransmission of the command data, the communication process module 55sends the write data so that the memory control circuit 136 of thememory device 130 receives the data one bit at a time. The write data issent in row order starting from the data to be written into Row A1.Specifically, the communication process module 55 sequentially sendsunit write data equivalent to 8 bits×4=32 bits (FIG. 14). A 32-bit unitof write data includes original data upper 8 bits UDn; inverted originaldata upper 8 bits /UDn representing inverted data of the original dataupper 8 bits UDn; original data lower 8 bits LDn; and inverted originaldata lower 8 bits /LDn representing inverted data of the original datalower 8 bits LDn (FIG. 14). The communication process module 55 sendsthe total of 32 bits in the order of: original data upper 8 bits UDn,inverted original data upper 8 bits /UDn, original data lower 8 bitsLDn, and inverted original data lower 8 bits /LDn (Steps S308 to S314).

In sync with the next rise of the clock signal CSCK following the end oftransmission of a unit of write data, the communication process module55 receives a 1-bit (either a “1” or a “0”) response signal from thememory control circuit 136 (FIG. 12: Step S316, FIG. 14). A “1” (highlevel) response signal (hereinafter also called an OK response signal)is a signal indicating that a unit of write data was received correctlyat the memory device 130, while a “0” (low level) response signal(hereinafter also called an NG response signal) is a signal indicatingthat a unit of write data may not be received correctly at the memorydevice 130. The reason for adopting a high level OK response signal inthe response signal is that, as noted earlier, the data signal line LD1is connected to low level potential via the pull-down resistor R1. Thisprevents that an high level OK response signal is erroneously input tothe communication process module 55 due to an communication errorcaused, for example, by faulty contact between the data terminal 260 andthe terminal 460 of the connection mechanism 400.

If the received response signal is not affirmative (FIG. 12: Step S318:NO), i.e. if the received response signal is NG response signal, thecommunication process module 55 carries out a prescribed error process(FIG. 12: Step S320) and terminate the write operation. The errorprocess may involve, for example, trying to resend the same unit ofwrite data, and if as a result of a certain number of retries only a NGresponse signal is obtained, notifying the main controller 40 of theerror. The main controller 40 would then display on the display panel ofthe console portion 70 a message prompting the user to recheckinstallation of the ink cartridge 100 for example.

If on the other hand the received response signal is affirmative (FIG.12: Step S318: YES), i.e. if an OK response signal is received, thecommunication process module 55 decides whether all of the data to bewritten to the memory device 130 has been sent (FIG. 12: Step S322). Ifall of the data to be written has been sent (FIG. 12: Step S322: YES),the communication process module 55 sends EOF (End of Frame) data to thememory device 130 (FIG. 12: Step S324), and terminate the writeoperation. Once the communication process module 55 terminates the writeprocess as depicted in FIG. 14, it transits the reset signal CRST fromhigh level to low level, and ceases to supply the clock signal CSCK. TheEOF data may be 8-bit data for example, and may be either significantdata or simple dummy data. If not all of the data to be written has beensent (FIG. 12: Step S322: NO), the communication process module 55returns to Step S308 and repeats the process discussed above for thenext unit of write data. For example, once the above process is carriedout for the first unit of write data UD1, /UD1, LD1, /LD1, thecommunication process module 55 carries out the above process for thesecond unit of write data UD2, /UD2, LD2, /LD2 for example.

The discussion now turns to processing that takes place on the memorydevice 130 (memory device processing) in response to a write operationto the memory device 130 on the printer 20 side discussed above. Thememory device processing in response to the write operation is the sameas that during a read operation from S210 to S250 in FIG. 10. In thecase of a write operation, in Step S240 of FIG. 10 the memory controlcircuit 136 of the memory device 130 receives a Write command.Consequently, the memory control circuit 136 having received the Writecommand executes the memory device write operation of Step S280 (FIG.10).

FIG. 15 is a flowchart depicting the process steps of a write operationon the memory device. After an operation code is received, if thecommand data is a Write command, then in the same manner as in the readoperation, the counter control module M16 controls the clock count valueof the address counter M13 so as to specify Row A1 as the initial rowtargeted for writing. Then, based on the address specified by the countvalue of the address counter M13, the read/write control module M14executes the write operation. Specifically, when the write operation isinitiated, the data send/receive module M15 of the memory controlcircuit 136, in sync with rise of the clock signal CSCK, sequentiallyreceives signals (1's or 0's) that appear on the data signal line LD1following the command data, and sequentially stores these in theregister. As a result, the data send/receive module M15 sequentiallyreceives the 32-bit write data, i.e. the original data upper 8 bits UDn,inverted original data upper 8 bits /UDn, original data lower 8 bitsLDn, and inverted original data lower 8 bits /LDn (FIG. 15: Steps S2802to S2808). After completing Step S2808, the data send/receive module M15changes the send/receive direction to the direction of sending from thememory device 130 to the sub-controller 50, and sends the sub-controller50 a response signal (either an NG response signal or OK responsesignal, discussed later) from the memory device 130.

When one unit of the 32-bit write data is received, the datadetermination module M19 decides whether or not the exclusive OR of anm-th value of the original data Dn and an m-th value of the invertedmirror data /dn is true “1” for all values of m (1≦m≦16), i.e. whetheror not it is FFFF (FIG. 15: Step S2810). The original data Dn referredto here is 16-bit data in which the original data upper 8 bits UDnreceived in the aforementioned Step S2802 constitute the upper bits, andthe original data lower 8 bits LDn received in the aforementioned StepS2806 constitute the lower bits. The inverted data /Dn referred to hereis 16-bit data in which the inverted original data upper 8 bits /UDnreceived in the aforementioned Step S2804 constitute the upper bits, andthe inverted original data lower 8 bits /LDn received in theaforementioned Step S2808 constitute the lower bits.

If the output of the exclusive OR operation (determination outcome bythe data determination module M19) is false “0” for any of the 16 bits,i.e. if it is not FFFF (FIG. 15: Step S2810: NO), the data send/receivemodule M15 sends an NG response signal (low level) to the communicationprocess module 55 of the sub-controller 50 (FIG. 15: Step S2812). Sincethe data signal line LD1 is maintained at a low level by the pull-downresistor R1 of the sub-controller 50 when there is no data transmissionon the line, it is permissible that the data send/receive module M15does not send any signal to the communication process module 55 of thesub-controller 50, in place of sending an NG response signal. In thiscase, the communication process module 55 also recognizes the low levelstate of the data signal line LD1 as an NG response signal. Accordingly,this is substantially equivalent to the case where an NG response signalis actually returned. Once the NG response signal has been sent, thewrite operation on the memory device terminates (abnormal termination).

If on the other hand the output of the exclusive OR operation(determination outcome by the data determination module M19) isaffirmative (true “1”) for all 16 bits, i.e. if it is FFFF (FIG. 15:Step S2810: YES), the data determination module M19 performs a paritycheck of the received 16-bit original data Dn and determine theconsistency of the data (FIG. 15: Step S2813). If the result of theparity check is that the data lacks consistency (FIG. 15: Step S2813:NO), the data send/receive module M15 sends an NG response signal (lowlevel) to the communication process module 55 of the sub-controller 50(FIG. 15: Step S2812). Since the data signal line LD1 is maintained at alow level by the pull-down resistor R1 of the sub-controller 50 whenthere is no data transmission on the line, it is permissible that thedata send/receive module M15 does not send any signal to thecommunication process module 55 of the sub-controller 50, therebysubstantially sending an NG response signal. Once the NG response signalis sent, the write operation on the memory device terminates (abnormaltermination). If on the other hand the result of the parity check isthat the data has consistency (FIG. 15: Step S2813: YES), the datasend/receive module M15 sends an OK response signal (high level) via thedata terminal to the communication process module 55 of thesub-controller 50 (FIG. 15: Step S2814).

The response signal (either an NG response signal or an OK responsesignal) is transmitted in sync with the next rise of the clock signalCSCK following reception of a unit of the 32-bit write data (FIG. 14).Specifically, after the memory device 130 has received a unit of the32-bit write data in sync with a clock signal sent from thesub-controller 50, the memory device 130 sends a response signal to thesub-controller 50 in sync with the next clock signal sent from thesub-controller 50. In the event that the ID comparator module M11 or thecommand parse module M12 determines that the ID data or the command dataCM includes a communication error, and the memory control circuit 136terminates operation without any meaningful process accordingly, thememory device 130 does not transmit any data during the response signaltransmission period. As described previously, the data signal line LD1is maintained at a low level by the resistor R1 of the sub-controller 50when there is no data transmission between the sub-controller 50 and thememory device 130. When the communication process module 55 detects alow level on the data signal line LD1 during the response signaltransmission period, the communication process module 55 decides that anNG signal is transmitted and a communication error is occurred. In otherwords, the transmission of NG signal in Step S2812 is performed whensome inconsistency is detected in the identification data or in thecommand data

If an OK response signal is sent, the copy data generation module M17 ofthe memory control circuit 136 generates mirror data dn which is a copyof the received 16-bit original data (FIG. 15: Step S2816).Specifically, in addition to the register for receiving original dataDn, the memory control circuit 136 is provided with a 16-bit registerfor storing mirror data dn, and the copy data generation module M17copies the original data Dn to generate the mirror data dn.

Next, the read/write control module M14 reads the previously stored datafrom the memory area targeted for writing (write-targeted memory area)of the original data Dn and the mirror data dn, whereupon the datadetermination module M19 performs a parity check of the read outpreviously stored data (FIG. 15: Step S2818). The write-targeted memoryarea for a single batch write operation is equal to a single row on thememory map in FIG. 7. As shown in FIG. 7, the upper 16 bits of thewrite-targeted memory area (an area equivalent to one row) constitute anoriginal data area for writing original data Dn, while parity data P isstored on the last bit of the original data area. The lower 16 bits ofthe write-targeted memory area (an area equivalent to one row)constitute a mirror data area for writing mirror data dn, while as inthe original data area, parity data P is stored on the last bit of themirror data area. In Step S2818, a parity check is performedrespectively for the previously stored data that has been stored in theoriginal data area of the write-targeted memory area, together with thepreviously stored data that has been stored in the mirror data area.

Once the parity check is finished, the read/write control module M14carries out writing of data to the write-targeted memory area (FIG. 15:Step S2820). Here, if no parity error is detected in either thepreviously stored data of the original data area or the previouslystored data of the mirror data area of the write-targeted memory area,the read/write control module M14 writes the original data that wasreceived in Steps S2802, S2806 to the original data area, and write themirror data that was generated in Step S2816 to the mirror data area,respectively. If on the other hand a parity error is detected in thepreviously stored data of the original data area of the write-targetedmemory area, but no parity error is detected in the previously storeddata of the mirror data area of the write-targeted memory area, theread/write control module M14 writes the previously stored data, ratherthan the received original data Dn, to the original data area, andwrites the mirror data that is generated in Step S2816 to the mirrordata area, respectively. If no parity error is detected in thepreviously stored data of the original data area of the write-targetedmemory area, but a parity error is detected in the previously storeddata of the mirror data area of the write-targeted memory area, theread/write control module M14 writes the original data that was receivedin Steps S2802, S2806 to the original data area, and writes thepreviously stored data to the mirror data area, respectively. If aparity error is detected in both the previously stored data of theoriginal data area and the previously stored data of the mirror dataarea of the write-targeted memory area, the read/write control moduleM14 rewrites the previously stored data to both the original data areaand the mirror data area. That is, for a memory area in which a parityerror is encountered, the read/write control module M14 performs arewrite of the previously stored data, and for a memory area in which noparity error is encountered, it will perform an update of the data.

When performing writing of data to a write-targeted memory area, thecommand parse module M12 of the memory control circuit 136 decideswhether all of the data for writing has been received (FIG. 15: StepS2822). The command parse module M12 may decide that all of the data forwriting has been received when it receives EOF data. Alternatively, itmay decide that all of the data for writing has been received when itdetects that the reset signal CRST has transitioned from high level tolow level. If all of the data for writing has been received (FIG. 15:Step S2822: YES), the memory control circuit 136 terminates the writeoperation. If not all of the data for writing has been received, thememory control circuit 136 returns to Step S2802 and repeat the processdescribed above for the next unit of write data. For example, once thefirst unit of write data D1 and /D1 is received and the above process iscarried out, next, the second unit of write data D2 and /D2 is receivedand the above process is carried out. In the present embodiment, becausethe address counter M13 specifies word addresses sequentially, followingRow A1 write operations takes place in order of Row A2, Row A3 . . . .Also, after transmission of an OK response signal (Step S2814), in orderto receive the next unit of write data, the data send/receive module M15sets the send/receive direction for data exchanged via the data terminalto the direction in which the memory device 130 receives data from thesub-controller 50. The steps of the flowchart depicted in FIG. 15 may beexecuted in a different order or in parallel, provided that no conflictsare created. For example, the memory control circuit 136 may generatemirror data prior to sending an OK signal; or it may generate the mirrordata while carrying out the parity check of previously stored data in aparallel operation.

As described above, during a write operation (FIG. 14), identificationdata ID, inverted identification data /ID, write command data CM,inverted write command data /CM, and a set of write data D1 and invertedwrite data /D1 of a prescribed size are transmitted in this order fromthe communication process module 55 to the memory device 130; afterwhich the second and subsequent sets of write data Dn and inverted writedata /Dn are transmitted repeatedly, one set at a time. In the exampleof FIG. 14, the data size of one set of write data Dn and inverted writedata /Dn is 32 bits; however, some other data size may be establishedinstead. From the time that reception of identification data ID startsuntil reception of the first set of write data D1 and inverted writedata /D1 is finished, the memory control circuit 136 of the memorydevice 130 does not send any OK or NG response signals indicative of aconsistency determination result for the received data to thecommunication process module 55, but rather sends an OK or NG responsesignal indicative of the consistency determination result to thecommunication process module 55 only after reception of the first set ofwrite data D1 and inverted write data /D1 is finished. Likewise, withregard to the second and subsequent sets of write data Dn and invertedwrite data /Dn, an OK or NG response signal indicative of thedetermination result for each set is sent from the memory controlcircuit 136 to the communication process module 55 each time thatreception of the set is completed. In this way, each time that one setof write data Dn and inverted write data /Dn of prescribed size isreceived, an OK or NG response signal indicative of the consistencydetermination result for the set is sent to the communication processmodule 55, so the reliability of communications between thecommunication process module 55 and the memory device 130 is enhanced.

In the initial phase of a write operation, from the time that receptionof identification data ID starts until reception of the first set ofwrite data D1 and inverted write data /D1 is finished, no dataconsistency determination results are sent to the communication processmodule 55, and thus the number of times that determination results aresent from the memory device 130 to the communication process module 55is reduced, and the write operation as a whole is carried outefficiently. Moreover, in write operations, consistency of theidentification data ID and inverted identification data /ID, andconsistency of the write command data CM and the inverted write commanddata /CM, are determined as in read operations (see Steps S220 to S245of FIG. 10). If the identification data ID and/or write command data CMlack consistency, the memory control circuit 136 terminates the processwithout carrying out writing of the received data to the memory cellarray 132. In this case, during the initial response signal transmissionperiod (the period following transmission of the data UD1, /UD1, LD1,/LD1), no OK response signal is sent from the memory device 130 to thecommunication process module 55 and an NG response signal is sent to thecommunication process module 55, so the communication process module 55recognizes that some sort of error is occurred. While the datatransmission direction does change around the time that the responsesignal (OK/NG response signal) is sent, in preferred practice changes indata transmission direction should be as infrequent as possible becauseof the possibility that a bus collision occurs. In the presentembodiment, through an arrangement whereby in the initial phase of awrite operation, no data consistency determination results are sent tothe communication process module 55 from the time that reception ofidentification data ID starts until reception of the first set of writedata D1 and inverted write data /D1 is finished, the frequency of changein data transmission direction is minimized, and the reliability andspeed of communication is enhanced.

Additionally, as depicted in FIG. 15 affirmative consistencydetermination results are generated only when the write data Dn and theinverted write data /Dn have a mutually inverted relationship and noparity errors are detected in the respective sets of data. By carryingout consistency determination in this way it is possible to furtherenhance the reliability of communications. That is, assume that one bitof the write data Dn and one bit of the inverted write data /Dn eachcontain an error at the same bit location, so that the determinationresult indicates that write data Dn and the inverted write data /Dn haveconsistency. Nevertheless, in such an instance, because the errors areidentified in the respective parity checks, it is possible to preventthe erroneous data from being written.

As will be appreciated from the discussion above, in the presentembodiment, the original data Dn corresponds to the first data in theappended claims, and the inverted data /Dn corresponds to the seconddata in the present invention. The mirror data do corresponds to thethird data in the present invention, and the inverted mirror data /dncorresponds to the fourth data in the present inventions. Transmissionof response signals (OK response signals and NG response signals)corresponds to the element of transmitting the determination result inthe present invention.

Memory Device Write Lock Operation:

FIG. 16 is a timing chart schematically depicting signals exchangedbetween the communication process module 55 of the printer 20 and thememory control circuit 136 of the memory device 130 during a write lockoperation of the memory device. The write lock operation is a processwhereby some portion of the rewriteable memory area in the memory map(FIG. 7) of the ferroelectric memory array 132 is changed to a writelock area, in row units. A row changed to a write lock area can nolonger be overwritten through access from an external device (e.g. thecommunication process module 55 of the sub-controller 50).

As in the read operation and write operation discussed above, thecommunication process module 55 first sends SOF data as a data signalCSDA (FIG. 16). As in the read operation and write operation discussedabove, following the SOF data, the communication process module 55 sendsidentification data in as a data signal CSDA (FIG. 16). Following theidentification data, the communication process module 55 sends commanddata as a data signal CSDA (FIG. 16). The command data sent in thisprocess is a Write Lock command representing a write lock operation. Insync with the next rise of the clock signal CSCK following completion oftransmission of the command data, the communication process module 55sends write lock-targeted address data AD and inverted writelock-targeted address data /AD in such a way that the memory controlcircuit 136 of the memory device 130 receives the data one bit at a timein synchronization with the clock signal (FIG. 16). The writelock-targeted address data AD is composed of 8-bit data for example, andidentifies a row to be changed from a write-enable area to a write lockarea. The inverted write lock-targeted address data /AD is 8-bit dataobtained by inverting the value of each bit of the write lock-targetedaddress data AD.

In sync with the next rise of the clock signal CSCK following completionof transmission of the write lock-targeted address data AD and invertedwrite lock-targeted address data /AD, the communication process module55 receives a 1-bit response signal (either a “1” or a “0”) from thememory device 130 (FIG. 16). As in write operations, a high levelresponse signal (OK response signal) is a signal indicating that thewrite lock-targeted address data AD and inverted write lock-targetedaddress data /AD are received correctly at the memory device 130, whilea low level response signal (NG response signal) is a signal indicatingthat the write lock-targeted address data AD and inverted writelock-targeted address data /AD are not received correctly at the memorydevice 130.

If the received response signal is an NG response signal, thecommunication process module 55 carries out a prescribed error processand terminate the write lock operation. The error process is a processidentical to the error process that takes place when an NG responsesignal is received in the write operation described above, for example.On the other hand, if the received response signal is an OK responsesignal, the communication process module 55 sends EOF (End of Frame)data to the memory device 130 and terminate the process (FIG. 16).

The discussion now turns to processing that takes place on the memorydevice 130 (memory device processing) in response to the write lockoperation to the memory device 130 at the printer 20 discussed above.The memory device processing in response to the write lock operation isdescribed in FIG. 10. In the case of the write lock operation, in StepS240 of FIG. 10 the memory control circuit 136 of the memory device 130receives a Write Lock command. Consequently, the memory control circuit136 having received the Write Lock command executes a write lockoperation of Step S270 (FIG. 10).

When the write lock operation starts, the read/write control module M14of the memory control circuit 136, in sync with rise of the clock signalCSCK, sequentially receives signals (1's or 0's) that appear on the datasignal line LD1 following the command data, and sequentially storesthese in the register. As a result, the memory control circuit 136sequentially receives the write lock-targeted address data AD andinverted write lock-targeted address data /AD.

The data determination module M19 decides whether or not the output ofan exclusive OR operation for the received write lock-targeted addressdata AD and inverted write lock-targeted address data /AD is true forall 8 bits of these data, i.e. whether or not it is 11111111 (FF). If itis found that the output of the exclusive OR operation is not FF, thedata send/receive module M15 sends an NG response signal (low level) tothe communication process module 55 of the sub-controller 50. Once theNG response signal is sent, the write lock operation on the memorydevice terminates (abnormal termination).

If on the other hand the output of the exclusive OR operation is true“1” for all 8 bits, i.e. if it is FF, the read/write control module M14changes the row of the rewriteable area identified by the writelock-targeted address data AD of the control area to a write lock area.Specifically, after receiving the operation code, if the type of accessis write lock, the counter control module M16 sets the counter value ofthe address counter M13 so as to select the lead row of the controlarea. The count then advances to select a row that includes a cellstoring a flag for the write lock-targeted address data AD in thecontrol area. After the row that includes a cell storing a flag for thewrite lock-targeted address data AD is selected by the address counterM13 as the row targeted for the write operation, the read/write controlmodule M14 updates the row so that the flag information of the cellcorresponding to the write lock-targeted address data AD changes from“0” to “1”. The read/write control module M14 updates the cell of thecontrol area storing the flag for the row of the rewriteable areaidentified by the write lock-targeted address data AD, thereby changingthe row of the rewriteable area identified by the write lock-targetedaddress data AD to a write lock area, and terminate the write lockoperation. Specifically, the read/write control module M14 changes thewrite lock flag information corresponding to the row identified by thewrite lock-targeted address data AD from “0” to “1”.

Printer Printing Operation:

In light of the processes relating to the memory devices 130 discussedabove, the discussion now turns to the printing operation in the printer20. FIG. 17 is a flowchart depicting the process steps in a printingoperation that is executed primarily by the main controller 40. Forconvenience in description, the following discussion of the printingoperation focuses upon a single ink cartridge 100, but in actualpractice the same processes are carried out for each ink cartridge 100installed in the printer 20.

The printing operation is initiated when the main controller 40 receivesa print request from the user via the computer 90 or the console portion70 (FIG. 17: Step S502). When a print request is received, the maincontroller 40 executes the read operation from the memory device 130discussed earlier, and read out ink information from the memory device130 of the ink cartridge 100 (FIG. 17: Step S504). The read out inkinformation includes at least the first ink consumption count value X,the second ink consumption count value Y, and ink end information M.

When the main controller 40 reads out the ink information, it decideswhether the value of the ink end information M indicates either the fullstate, the low state, or the end state mentioned previously (FIG. 17:Step S506). If the main controller 40 decides that the ink endinformation M indicates the end state (FIG. 17: Step S506: E), itcarries out an ink end alert directed to the user (FIG. 17: Step S508).The ink end alert may involve, for example, displaying on the displaypanel of the console portion 70 a message prompting the user to replacethe ink cartridge 100.

If the main controller 40 decides that the ink end information Mindicates the low state (FIG. 17: Step S506: L), it decides whether thevalue of the difference (X−Y) between the first ink consumption countvalue X and the second ink consumption count value Y is equal to orgreater than a second threshold value Vref2 (FIG. 17: Step S510). Aswill be discussed later, the row storing the second ink consumptioncount value Y in the memory device 130 is write locked at the point thatink end was detected, so the second ink consumption count value Y willnot be updated. If the value of (X−Y) is equal to or greater than thesecond threshold value Vref2 (FIG. 17: Step S510: YES), the maincontroller 40 updates the value of the ink end information M of thememory device 130 to the end state (FIG. 17: Step S512). Specifically,the main controller 40 executes the write operation to the memory device130 discussed previously, and update the value of the ink endinformation M to “11”. After updating the value of the ink endinformation M, the main controller 40 carries out the ink endnotification described above (FIG. 17: Step S508).

On the other hand, if the main controller 40 decides that the ink endinformation M indicates the full state (FIG. 17: Step S506: F) or thatthe value of (X−Y) is less than the second threshold value Vref2 (FIG.17: Step S510: NO), it carries out a predetermined amount of printing ofthe print job requested by the print request (FIG. 17: Step S514).

Once the predetermined amount of printing is carried out, the maincontroller 40 calculates a new ink consumption count value (FIG. 17:Step S516). Specifically, on the basis of the particulars of executionof the predetermined amount of printing, the main controller 40estimates the amount of ink consumed in the course of the predeterminedamount of printing. The main controller 40 then adds a count value,equivalent to the estimated amount of ink consumed, to the first inkconsumption count value X that was read out from the memory device 130in Step S504, to arrive at a new ink consumption count value.

Once the new ink consumption count value is calculated, the maincontroller 40 drives the sensor 110 (FIG. 17: Step S518). On the basisof the result of driving the sensor 110, the main controller 40 decideswhether the remaining ink level in the ink cartridge 100 is equal to orgreater than the first threshold value Vref1 (i.e. full) or less thanthe first threshold value Vref1 (i.e. low) (FIG. 17: Step S520).

If the remaining ink level in the ink cartridge 100 is determined to beequal to or greater than the first threshold value Vref1 (FIG. 17: StepS520: F), the main controller 40 will update the first ink consumptioncount value X and the second ink consumption count value Y that aresaved to the memory device 130, to the new ink consumption count valuethat was calculated in Step S516 (FIG. 17: Step S522). Specifically, themain controller 40 executes the write operation discussed earlier,accessing the memory device 130 and overwriting the first inkconsumption count value X and the second ink consumption count value Ywith the new ink consumption count value. As a result, the first inkconsumption count value X and the second ink consumption count value Ywill be the same.

On the other hand, if the remaining ink level in the ink cartridge 100is determined to be less than the first threshold value Vref1 (FIG. 17:Step S520: L), the main controller 40 verifies whether the memory areastoring the second ink consumption count value Y (FIG. 7: Row A2 of thememory map) is a write lock area (i.e. with reference to the write lockflag stored in a memory area of the SRAM 551 which corresponds to thecontrol area of the memory device 130); and in the event it is found notto be a write lock area, carries out a second ink consumption countvalue lock operation to place a write lock on the row storing the secondink consumption count value Y (FIG. 17: Step S524). The second inkconsumption count value lock operation is carried out using the writelock operation for the memory device 130 discussed earlier. Once thesecond ink consumption count value lock operation is carried out, thevalue of the second ink consumption count value Y in the memory device130 is no longer modifiable. Consequently, the value of the second inkconsumption count value Y in the memory device 130 will be held at theink consumption count value that obtained just prior to the time thatthe remaining ink level was first detected to be lower than the firstthreshold value Vref1, through driving of the sensor 110.

When the second ink consumption count value lock operation is completed,the main controller 40 executes the write operation discussed earlier onthe first ink consumption count value X in the memory device 130,thereby updating it to the new ink consumption count value that wascalculated in Step S516 (FIG. 17: Step S526). At this time, due to thewrite lock, the second ink consumption count value is not updated.

When the first ink consumption count value X is updated, the maincontroller 40 decides whether the value of the difference (X−Y) betweenthe first ink consumption count value X and the second ink consumptioncount value Y is equal to or greater than a second threshold value Vref2(FIG. 17: Step S528). Here, the first ink consumption count value X isthe value that was updated in Step S526. Meanwhile, the second inkconsumption count value Y is the newer of the value that was read out inStep S504 or the values that were updated in Step S522. If thedifference (X−Y) is equal to or greater than the second threshold valueVref2 (FIG. 17: Step S528: YES), the main controller 40 updates thevalue of the ink end information M of the memory device 130 to the endstate (Step S512), and carries out the ink end alert discussed above(FIG. 17: Step S508).

After the first ink consumption count value X and the second inkconsumption count value Y are updated in Step S522, or if in Step S528the value of (X−Y) is found to be less than the second threshold valueVref2 (FIG. 17: Step S528: NO), the main controller 40 decides whetherthe print job based on the print request is completed (FIG. 17: StepS530). If the print job is completed (FIG. 17: Step S530: YES), theprinting operation terminates. If the print job is not completed, thesystem returns to Step S514, and a predetermined amount of printing iscarried out again.

According to the present embodiment discussed above, during a writeoperation to the memory device 130, the memory device 130 verifies theconsistency of the original data Dn that is to be written to the memorycell array 132 and the inverted data /Dn, and for each 16 bits oforiginal data Dn transmits a response signal indicating if there isconsistency. As a result, reliability of communication between thesub-controller 50 and the memory device 130 is enhanced. If the originaldata Dn and the inverted data /Dn lack consistency, the memory device130 does not write the original data Dn to the ferroelectric memoryarray 132, so erroneous updating of the ferroelectric memory array 132is avoided. Moreover, during write operations to the memory device 130,because the original data Dn and the inverted data /Dn have an invertedbit relationship to one another, if for example there is encountered acommunication error such that only low level or high level appears onthe data signal line LD1 owing to a contact fault between the dataterminal 260 of the ink cartridge 100 and the corresponding terminal onthe printer 20, the communication error is detected in a reliablemanner. Moreover, because consistency (presence or lack of communicationerrors) of the original data Dn and the inverted data /Dn is determinedthrough an exclusive OR operation carried out on each bit of theoriginal data Dn and the inverted data /Dn, highly reliable detection ofcommunication errors is accomplished easily.

Furthermore, according to the present embodiment, during a readoperation from the memory device 130 original data Dn, together withinverted data /Dn which is equal in size to the original data Dn butwith each bit inverted, are sent from the memory device 130 to thesub-controller 50. At the sub-controller 50, the presence or lack ofcommunication errors is then determined by checking the consistency ofthe original data Dn and the inverted data /Dn. As a result, reliabilityof communication between the sub-controller 50 and the memory device 130is enhanced. Consequently, problems such as erroneous operation of theprinter 20 are kept to a minimum. Moreover, during read operations fromthe memory device 130, because the original data Dn and the inverteddata /Dn have an inverted bit relationship to one another, if forexample there is encountered a communication error such that only lowlevel or high level appears on the data signal line LD1 owing to acontact fault between the data terminal 260 of the ink cartridge 100 andthe corresponding terminal on the printer 20, the communication error isdetected in a reliable manner. Further, during read operations from thememory device 130, because the memory device 130 sends thesub-controller 50 mirror data dn which is substantially identical to theoriginal data Dn, and inverted mirror data /dn which is substantiallyidentical to the inverted data /Dn, even if the original data Dn and theinverted data /Dn lack consistency owing to a communication error forexample, as long as the mirror data dn and the inverted mirror data /dnhave consistency, processing can continue on the printer 20 using eitherthe mirror data dn or the inverted mirror data /dn, thus enhancing therobustness of the system with respect to communication errors. Further,in the memory device 130, mirror data dn is stored together withoriginal data Dn in the ferroelectric memory array 132, and both aresent to the printer 20. As a result, even if a cell error is occurred ineither the original data area or the mirror data area of theferroelectric memory array 132, normal operation may continue on theprinter 20, using the data stored in the area in which the cell errordid not occur. Robustness of the system with respect to cell errors isenhanced thereby, thus dramatically reducing memory device 130 failurerates.

Further, when the printer 20 in the present embodiment receives originaldata Dn, inverted data /Dn, mirror data dn, and inverted mirror data/dn, it first performs a consistency check of the original data Dn andthe inverted mirror data /dn; and if consistency is lacking, checks theconsistency of the original data Dn and the inverted data /Dn, and theconsistency of the mirror data dn and the inverted mirror data /dn.Then, if the original data Dn and the inverted mirror data /dn lackconsistency, but the original data Dn and the inverted data /Dn haveconsistency and the mirror data dn and the inverted mirror data /dn haveconsistency, it determines that a cell error is occurred. If theoriginal data Dn and the inverted mirror data /dn lack consistency, andmoreover the original data Dn and the inverted data /Dn lack consistencyor the mirror data dn and the inverted mirror data /dn lack consistency,it determines that a communication error is occurred. By so doing theprinter 20 can correctly ascertain the type of the error, and performappropriate processing according to the error type.

Further, in the present embodiment, in the memory map of theferroelectric memory array 132 (FIG. 7), actual data and parity data arestored in the original data area, and actual data and parity data arestored in the mirror data area as well. During a read operation from therewriteable area, the actual data (upper 15 bits) and the parity data(lower 1 bit) stored in the original data area are sent from the memorydevice 130 to the sub-controller 50, and the actual data (upper 15 bits)and the parity data (lower 1 bit) stored in the mirror data area aresent from the memory device 130 to the sub-controller 50. Consequentlythe printer 20 having received this data then performs a parity check ofthe actual data that was stored in the original data area, and perform aparity check of the actual data that was stored in the mirror data area.Even if a parity error is occurred either in the actual data that wasstored in the original data area or in the actual data that was storedin the mirror data area, the main controller 40 is able to continuenormal operation using the set of actual data in which no parity erroris occurred. As a result, robustness of the system against communicationerrors and cell errors may be enhanced.

In write operations in the present embodiment, for previously storeddata in a write-targeted area, the memory device 130 carries out aparity check of the 16 bits stored in the original data area and the 16bits stored in the mirror data area, respectively. As a result, in anarea in which a parity error is detected, the previously stored data isrewritten; whereas in an area in which no parity error is detected, newdata is written. Because an area in which a parity error is detected canbe assumed to have a problem with a memory cell, the parity check mayalso be recognized as a means for detecting memory area problem. As aresult, data updating is not performed in an area in which a problem isoccurred, so unanticipated difficulties that may result from updatingdata in an area that includes a problem may be avoided. Moreover, in acell that is experiencing a cell error, by rewriting previously storeddata to an area in which a parity error is detected, change in data dueto a data retention fault may be avoided. A data retention fault refersto a fault whereby the saved data value in a memory cell changes due togradual dissipation of charge. If owing to a data retention fault, datachanges in an area in which a cell error is assumed to have occurred,parity consistency may happen by chance, posing a risk that the cellerror is not correctly detected. Further, in the printer 20 according tothe present embodiment, if through driving of the sensor 110 it isdetermined that the remaining ink level of the ink cartridge 100 is lessthan the first threshold value Vref1, a prohibit request (write lockoperation) is carried out for the memory area of the memory device 130storing the second ink consumption count value Y, so that the second inkconsumption count value Y will not be updated. As a result, after theprohibit request is issued, the memory device 130 no longer acceptsrequests to update the second ink consumption count value Y. As aresult, the second ink consumption count value Y is maintained at theink consumption count value that obtained just prior to the time thatthe sensor detected that the remaining ink level was lower than thefirst threshold value Vref1. The second ink consumption count value Y isthus prevented from being updated in error. Further, because the firstink consumption count value X continues to be updated even afterupdating of the second ink consumption count value Y is suspended, theink consumption level is accurately recognized from the value of (X−Y)even after the sensor 110 detects that the remaining ink level is lowerthan the first threshold value Vref1. As a result, an ink end point isdetermined with good accuracy, making it possible for the ink containedin the ink cartridge 100 to be used to the end without any waste. Aswill be appreciated from the discussion above, in the presentembodiment, the inverted data generation module M18 corresponds to thedata generation section in the present invention.

B. Modified Embodiments Modified Embodiment 1

In the preceding embodiment, inverted data /Dn is used as an example of“the data generated on the basis of the original data Dn”, but nolimitation thereto is implied. For example, a value obtained throughaddition of a given value to the original data Dn, a value obtainedthrough subtraction of a given value, a value obtained throughmultiplication by a given value, or the like may also be used as datafor checking consistency with the original data Dn. Generally, itsuffices for the original data Dn and the data generated from theoriginal data Dn to have a prescribed correlation such that the presenceor lack of this prescribed correlation between the original data Dn andthe data generated from the original data Dn can be determined. Inpreferred practice, the original data Dn and the data generated from theoriginal data Dn have identical data size.

Modified Embodiment 2

In the write operation of the preceding embodiment, 32 bit data composedof original data upper 8 bits UDn, inverted mirror data upper 8 bits/Udn, original data lower 8 bits LDn, and inverted mirror data lower 8bits /Ldn are transmitted in that order from the sub-controller 50 tothe memory device 130; however, the order of transmission may bemodified as desired, and it is acceptable to first transmit 16 bits oforiginal data Dn1, followed by transmission of 16 bits of inverted data/Dn. Also, the inverted data may be sent first, and the original datasent afterwards.

Modified Embodiment 3

In the write operation of the preceding embodiment, 32 bits of originaldata and inverted data are employed as a single unit of data, and eachtime that transmission of one unit of data from the sub-controller 50 tothe memory device is finished, a response signal is returned from thememory device to the sub-controller 50; however, the data length of theunit of data is may be modified as desired, and a single data unit mayinclude 64 bits of original data and inverted data, or a single dataunit may include 16 bits of original data and inverted data.

Modified Embodiment 4

In the preceding embodiment, the sub-controller 50 of the printer 20 isused as the host circuit; however, any circuit, such as a computor, maybe used as the host circuit. In the preceding embodiment, the memorydevice 130 of an ink cartridge 100 is used as the memory device, but anynonvolatile memory device may be used. In this case, the invention maybe implemented effectively in an arrangement whereby the host circuitand the memory device are electrically connected via circuit terminalsthat are electrically connected to the host circuit, and memory deviceterminals that are electrically connected to the memory device and thatare detachably attachable to the circuit terminals. By so doing,communication errors arising from faulty contact between memory deviceterminals and circuit terminals may be detected, and the reliability ofcommunication between the host circuit and the memory device may beenhanced.

Modified Embodiment 5

In the preceding embodiment, the ferroelectric memory array 132 isprovided with both an original data area and a mirror data area;however, only an original data would suffice. In this case, the memorycontrol circuit 136 may be provided with a read copy data generationsection adapted to copy data stored in the original data area togenerate mirror data dn (copy data), and with an inverted datageneration section adapted to invert each bit of the data stored in theoriginal data area to generate inverted data /Dn and inverted mirrordata /dn. Then, during the read operation at the memory device 130, thedata send/receive module M15 of the memory control circuit 136 sends thedata that is stored in the original data area as original data Dn to thesub-controller 50; and sends the sub-controller 50 the mirror data dn,the inverted data /Dn, and the inverted mirror data /dn which aregenerated from the original data Dn. The data send/receive module M15,after storing the data read out from the original data area in aregister, may send it as original data, and then send other data storedin the register as mirror data. In the fifth modified embodiment, thecopy data generation module and the inverted data generation modulecorrespond to the data generation section in the present invention.

Modified Embodiment 6

In the preceding embodiment, the ferroelectric memory array 132 has anoriginal data area and a mirror data area; however, the ferroelectricmemory array 132 may instead have an original data area and an inverteddata area. In this case, the read/write control module M14 writes theoriginal data Dn in the original data area, and writes the inverted data/Dn in the inverted data area. During read operations, the datasend/receive module M15 of the memory control circuit 136 sends to thesub-controller 50 as original data Dn the data stored in the originaldata area, and as inverted data /Dn the data stored in the inverted dataarea; and sends to the sub-controller 50 as mirror data dn the datawhich is read from this same original data area, and as inverted mirrordata /dn the data which is read from this same inverted data area. Inthis case as well, the host circuit is able to detect communicationerrors through exclusive OR operations. It is possible to detect theoccurrence of memory cell errors by carrying out a parity check.

Modified Embodiment 7

In the preceding embodiment, the ferroelectric memory array 132 has anoriginal data area and a mirror data area; however, the ferroelectricmemory array 132 may instead have an original data area for storingoriginal data Dn, and inverted data area for storing inverted data /Dnof the original data Dn, a mirror data area for storing mirror data dnof the original data Dn, and an inverted mirror data area for storinginverted mirror data /dn which is inverted data of the mirror data dn.In this case, the read/write control module M14 and the datasend/receive module M15 of the memory control circuit 136 read out thestored data as-is and transmit it.

Modified Embodiment 8

In the read operation in the preceding embodiment, original data Dn,inverted data /Dn, mirror data dn, and inverted mirror data /dn aretransmitted from the memory device 130 to the sub-controller 50;however, it would suffice to transmit original data Dn and inverted data/Dn only, omitting transmission of mirror data dn and inverted mirrordata /dn. Alternatively, it would suffice to transmit original data Dnand mirror data dn only, omitting transmission of inverted data /Dn andinverted mirror data /dn.

Modified Embodiment 9

In the write operation in the preceding embodiment, both actual data andparity data for storage in the memory map of the ferroelectric memoryarray 132 are generated on the printer 20 and transmitted to the memorydevice 130. As an alternative, it is permissible that the printer 20generates only the actual data and transmits it to the memory device130, while the parity data is generated on the memory device 130. Inthis case, the memory control circuit 136 may be provided with a parityacquisition module for generating 1-bit parity data matching the 15 bitsof actual data sent from the printer 20.

Modified Embodiment 10

In the write operation in the preceding embodiment, the memory device130 performs rewriting of the previously stored data to areas in whichparity errors are detected, but a possible alternative would be to notwrite data to areas in which parity errors are detected.

Modified Embodiment 11

In the preceding embodiment, the ferroelectric memory array 132 of thememory device 130 stores a first ink consumption count value X and asecond ink consumption count value Y that represent the amount of inkconsumption; however, remaining level information representing theremaining ink level may also be stored. In this case, the initial valueof the remaining level information represents the amount of ink fillingthe ink cartridge 100. During printing operations, the printer 20overwrites the remaining level information stored in the ferroelectricmemory array 132 with remaining level information in the direction ofdecreasing the remaining level, according to the amount of ink consumedin printing. In this case, it is preferable for the memory area storingthe remaining level information to be established in a decrement area. Adecrement area refers to an area that only allows numerical values to beoverwritten in the decreasing direction, and does not allow numericalvalues to be overwritten in the increasing direction. Like the incrementarea in the embodiment, such a decrement area is preferably establishedby writing decrement flag information to the read-only area.

Modified Embodiment 12

In the preceding embodiment, the second ink consumption count value Yand the first ink consumption count value X are respectively stored inthe ferroelectric memory array 132, and ink end is determined on thebasis of the difference between the first ink consumption count value Xand the second ink consumption count value Y. Alternatively, only thesecond ink consumption count value Y may be stored in the ferroelectricmemory array 132. In this case, processes would take place in the samemanner as the embodiment, but with the first ink consumption count valueX stored in nonvolatile memory provided on the printer 20.

Modified Embodiment 13

While the preceding embodiment employs a printer and ink cartridges ofink-jet format, it would also be acceptable to employ a liquid jettingapparatus adapted to jet or eject a liquid other than ink, and liquidreceptacles for supplying the liquid to the liquid jetting apparatus.Herein, the term liquid is used to include a liquid state bodycontaining particles of a functional material dispersed in a medium; ora gel or similar fluid state body. For example, there may be employed aliquid jetting apparatus adapted to jet a liquid containing an electrodematerial, coloring matter, or other matter in dispersed or dissolvedform, that is used in the manufacture of liquid crystal displays, EL(electroluminescence) displays, field emission displays, or colorfilters; a liquid jetting apparatus adapted to jet bioorganic substancesused in biochip manufacture; or a liquid jetting apparatus adapted tojet a liquid as a specimen used as a precision pipette. Additionalexamples are a liquid jetting apparatus for pinpoint jetting of alubricant into a precision instrument such as a clock or camera; aliquid jetting apparatus adapted to jet a solution of anultraviolet-curing resin or other transparent resin onto a substrate forthe purpose of forming a micro semi-spherical lens (optical lens) foruse in an optical communication component etc.; or a liquid jettingapparatus adapted to jet an acid or alkali etchant solution for etchinga circuit board, etc.; as well as liquid receptacles adapted to supplyliquid to these kinds of liquid jetting apparatus. The present inventionmay be implemented in any one of the above types of jetting devices andliquid receptacles. No limitation to printers of ink-jet format isimposed, and a laser printer and toner cartridge for printing withprinting material such as toner may also be employed.

Modified Embodiment 14

Some of the arrangements that are implemented through hardware in thepreceding embodiment may instead be implemented through software, andconversely some of the arrangements that are implemented throughsoftware may instead be implemented through hardware.

Modified Embodiment 15

In the preceding embodiment, a sensor 110 that uses a piezoelectricelement is employed, but it would be possible for example to insteademploy an oscillator device such as an oscillator circuit designed toconstantly return a response signal whose frequency indicates that inkis present; or to employ a processor such as a CPU or ASIC, or a simplerIC, to carry out exchanges with the sub-controller 50. The presentinvention may also be implemented in an ink cartridge 100 of a typelacking a sensor, and having only a memory device.

Modified Embodiment 16

In the preceding embodiment, a single ink tank constitutes a single inkcartridge, but instead a plurality of ink tanks may constitute a singleink cartridge.

Modified Embodiment 17

In the preceding embodiment, the liquid supply unit is an ink cartridgeto whose receptacle body the board is secured, and the board thuslyunified with the receptacle body is installed in the holder provided tothe print head unit; however, the liquid supply unit embodying thepresent invention may instead be an ink cartridge of a design in which acover to which the board is secured, and a receptacle body containingthe liquid, are installed separately in the holder. In one exemplaryarrangement, after the cover having the board secured thereto isinserted and installed in the holder in a prescribed insertiondirection, the receptacle body is then installed in the holder. In thiscase, there may be employed in arrangement whereby only the inkreceptacle body is replaced when the ink inside the receptacle body isdepleted, and the ink consumption information (the first second inkconsumption count value X and the second ink consumption count value Y)saved in the memory device 130 is reset in association with replacement.

Modified Embodiment 18

In the preceding embodiment, the liquid supply unit is installed in theholder of the print head unit and supplies ink directly to the printhead from the ink supply portion; however in another possiblearrangement, the liquid supply unit may be installed at a locationinside the liquid jetting apparatus situated away from the head, and inkmay be supplied to the head through a tube connecting the liquid supplyunit to the ink supply portion.

Modified Embodiment 19

In the preceding embodiment, the memory device 130 is described as beinga semiconductor memory device furnished with a ferroelectric memory cellarray 132, but is not limited thereto and may instead be a semiconductormemory device that does not use ferroelectric memory cells (e.g. EEPROMor flash memory). Memory devices other than semiconductor memory devicesmay also be used.

Modified Embodiment 20

In the preceding embodiment, the main controller 40 and thecommunication process module 55 are separate arrangements, but they mayinstead be implemented as an integrated controller.

Modified Embodiment 21

In the preceding embodiment, in the course of communications between thememory device 130 and sub-controller 50, the memory device 130 ispresented with a reset signal CRST from the sub-controller 50; however,the element of supplying a reset signal CRST may be omitted. In thiscase, the reset terminal 240 of the memory device 130, the terminal 440on the printer 20 corresponding to the reset terminal 240, and the resetsignal line LR1 would be dispensed with. In this case, initialization ofthe memory device 130 may take place autonomously when the memory device130 is supplied with power supply voltage CVDD and starts up forexample. Having initialized at startup, the memory device 130 maysubsequently operate in response to the clock signal CSCK and datasignals CSDA received from the sub-controller 50, in the same way as inthe embodiment.

Modified Embodiment 22

In the preceding embodiment, the memory control circuit 136 of thememory device 130 includes the ID comparator module M11, the commandparse module M12, and the data determination module M19. However, the IDcomparator module M11, the command parse module M12, and the datadetermination module M19 may be implemented as respective separatehardware circuits. Alternatively, a part of or the entirety of thesemodules may be implemented as common hardware circuitry.

While the present invention is shown herein in terms of a preferredembodiment and modified embodiments thereof, the present invention isnot limited to the embodiment and modified embodiments herein, and maybe embodied in various other forms without departing from the spiritthereof.

1. A memory device electrically connectable to a host circuit,comprising: a nonvolatile data memory section; a read/write controlsection that reads a first data from the nonvolatile data memorysection, the first data having a prescribed data amount; and a datatransmission section that transmits to the host circuit the first datatogether with second data, wherein the second data is different from thefirst data and has prescribed correlation with content of the firstdata, the second data having an identical data amount to the data amountof the first data.
 2. The memory device according to claim 1, furthercomprising: a data generation section that generates the second datausing the first data.
 3. The memory device according to claim 1, whereinthe first data and the second data each are binary signals of n bitswhere n is an integer equal to or greater than 1, and the second data isinverted data that inverts each bit of the first data.
 4. The memorydevice according to claim 3, wherein the integer n is an even number,and the data transmission section transmits, in synchronism with a clocksignal, an upper n/2 bits of the first data, an upper n/2 bits of thesecond data, a lower n/2 bits of the first data, and a lower n/2 bits ofthe second data, in that order.
 5. The memory device according to claim1, wherein the data transmission section additionally transmits to thehost circuit third data that is substantially identical to the firstdata, and fourth data that is substantially identical to the seconddata.
 6. The memory device according to claim 5, wherein the nonvolatiledata memory section has a first memory area for storing the first data,and a second memory area for storing the third data.
 7. The memorydevice according to claim 5, further comprising a data generationsection that generate the second data from the first data, and togenerate the fourth data from the third data.
 8. The memory deviceaccording to claim 5, wherein the first data, the second data, the thirddata, and the fourth data each are binary signals of m bits where m isan integer equal to or greater than 1; the third data is copy datacopied from the first data, the second data is inverted data thatinverts each bit of the first data, and the fourth data is inverted datathat inverts each bit of the third data.
 9. The memory device accordingto claim 8, wherein the integer m is an even number, and the datatransmission section transmits, in synchronism with a clock signal, anupper m/2 bits of the first data, an upper m/2 bits of the second data,a lower m/2 bits of the first data, a lower m/2 bits of the second data,an upper m/2 bits of the third data, an upper m/2 bits of the fourthdata, a lower m/2 bits of the third data, and a lower m/2 bits of thefourth data, in that order.
 10. The memory device according to claim 5,further comprising a data generation section that generates the seconddata, the third data, and the fourth data from the first data.
 11. Thememory device according to claim 5, further comprising a first memoryarea for storing the first data, and a second memory area for storingthe third data.
 12. The memory device according to claim 5, furthercomprising: a data generation section that generates the third data fromthe first data, and generates the fourth data from the second data. 13.The memory device according to claim 1, wherein the host circuit and thememory device are adapted to be electrically connected via circuit-sideterminals that are electrically connected to the host circuit, andmemory-device-side terminals that are electrically connected to thememory device and detachably attachable to the circuit-side terminals.14. A host circuit electrically connectable to the memory deviceaccording to claim 1, comprising: a data reception section that receivesthe first data and the second data from the memory device; and adetermination section that determines whether the first data and thesecond data have the prescribed correlation.
 15. A host circuitelectrically connectable to the memory device according to claim 3,comprising: a data reception section that receives the first data andthe second data from the memory device; and a determination section thatoutputs an affirmative determination result if an exclusive OR outcomeof an m-th value of the first data and an m-th value in the second datais true for all the n bits where m is an integer such that 1≦m≦n; andoutputs a negative determination result if the exclusive OR outcome isfalse for any one of the n bits.
 16. A host circuit electricallyconnectable to the memory device according to claim 8, comprising: adata reception section that receives the first data, the second data,the third data, and the fourth data from the memory device; and a firstdetermination section that carries out a first determination to outputan affirmative determination result if an exclusive OR outcome of a k-thvalue of the first data and a k-th value of the fourth data is true forall the m bits where k is an integer such that 1≦k≦m, or to output anegative determination result if the exclusive OR outcome is false forany one of the m bits.
 17. The host circuit according to claim 16,further comprising a second determination section that carries out asecond determination in instances where the determination result of thefirst determination is negative, wherein the second determinationsection determines that an error has occurred in the nonvolatile datamemory section of the memory device if an exclusive OR outcome of a k-thvalue of the first data and a k-th value of the second data is true forall the m bits, and also an exclusive OR outcome of a k-th value of thethird data and a k-th value of the fourth data is true for all the mbits, and the second determination section determines that acommunication error has occurred between the memory device and the hostcircuit if the exclusive OR outcome of the k-th value of the first dataand the k-th value of the second data is false for any one of the mbits, or if the exclusive OR outcome of the k-th value of the third dataand the k-th value of the fourth data is false for any one of the mbits.
 18. A board detachably and electrically connectable to a liquidjetting apparatus, comprising: a nonvolatile data memory section; aread/write control section that reads a first data from the nonvolatiledata memory section, the first data having a prescribed data amount; anda data transmission section that transmits to the liquid jettingapparatus the first data together with second data, wherein the seconddata is different from the first data and has prescribed correlationwith content of the first data, and is identical in size to the firstdata, the second data having an identical data amount to the data amountof the first data.
 19. A liquid receptacle detachably installable in aliquid jetting apparatus, comprising: a nonvolatile data memory section;a read/write control section that reads a first data from thenonvolatile data memory section, the first data having a prescribed dataamount; and a data transmission section that transmits to the liquidjetting apparatus the first data together with second data, wherein thesecond data is different from the first data and has prescribedcorrelation with content of the first data, and is identical in size tothe first data, the second data having an identical data amount to thedata amount of the first data.
 20. A method of transmitting data storedin a nonvolatile data memory section to a host circuit, comprising thesteps of: reading a first data from the nonvolatile data memory section,the first data having a prescribed data amount; and transmitting to thehost circuit the first data together with second data, wherein thesecond data is different from the first data and has prescribedcorrelation with content of the first data, and is identical in size tothe first data, the second data having an identical data amount to thedata amount of the first data.
 21. A system comprising a host circuitand a memory device electrically connectable to the host circuit,wherein the memory device includes: a nonvolatile data memory section; aread/write control section that reads a first data from the nonvolatiledata memory section, the first data having a prescribed data amount; anda data transmission section that transmits to the host circuit the firstdata together with second data, wherein the second data is differentfrom the first data and has prescribed correlation with content of thefirst data, and is identical in size to the first data, the second datahaving an identical data amount to the data amount of the first data,and the host circuit includes: a data reception section that receivesthe first data and the second data from the memory device; and adetermination section that determines whether the first data and thesecond data have the prescribed correlation.